Following a request from the post Lr-mame 20xy and handheld games
Here is a tutorial to create 7 new systems with MAME standalone. The systems are:

• Konami Handheld
• "All in one" handheld and Plug & Play (concept like 100 games in one cartridge)
• Game & Watch (with madrigal and MAME romset)
• Tiger Handheld
• Tiger R-Zone
• Classic Handheld (non-game & watch from madrigal and all other manufacturers in the MAME romset such as Coleco, Entex, etc.)
• JAKKS Pacific TV Games ----> New edit: Here's a tutorial to add more games with Jakks Game Key files : How to run Jakks Game Key files on RetroPie credit goes to: @JimmyFromTheBay
  New edit: : For gamelist.xml and Artworks for those systems, you can use Development of module-script generator for lr-mess, lr-mame and mame standalone approach or get them here (gamelist, artworks)

1 - Install MAME (standalone from binary) from experimental section in Retropie Setup
2 - Get MAME Romset (most recent) and get games from the lists in the following post see First Reply in this post (below).
3 - Create 7 games folders in /home/pi/RetroPie/roms for systems above (gameandwatch maybe already exist):
NEW EDIT: For steps 3 to 9, you can use the script here: Development of module-script generator for lr-mess and mame standalone <--------- (Highly recommended)
all_in1
classich
jakks
konamih
tigerrz
tigerh
gameandwatch (if not already created)

4 - Modify or Create a theme (see Theme tutorial) and add pictures in your config folders (launching.png) for when your games load
5 - go in /opt/retropie/configs/mame and open mame.ini with Notepad++ via FileZilla and replace the lines by this:

rompath /home/pi/RetroPie/roms/mame;/home/pi/RetroPie/roms/arcade;/home/pi/RetroPie/BIOS/mame;/home/pi/RetroPie/BIOS;/home/pi/RetroPie/roms/tigerh;/home/pi/RetroPie/roms/gameandwatch;/home/pi/RetroPie/roms/tigerrz;/home/pi/RetroPie/roms/pong;/home/pi/RetroPie/roms/konamih;/home/pi/RetroPie/roms/classich;/home/pi/RetroPie/roms/atomiswave;/home/pi/RetroPie/roms/naomi;/home/pi/RetroPie/roms/all_in1;/home/pi/RetroPie/roms/jakks
hashpath /opt/retropie/emulators/mame/hash
samplepath /home/pi/RetroPie/roms/mame/samples;/home/pi/RetroPie/roms/arcade/samples
artpath /home/pi/RetroPie/roms/mame/artwork;/home/pi/RetroPie/roms/arcade/artwork;/home/pi/RetroPie/BIOS/mame/artwork
ctrlrpath /opt/retropie/emulators/mame/ctrlr
pluginspath /opt/retropie/emulators/mame/plugins
languagepath /opt/retropie/emulators/mame/language
cfg_directory /home/pi/RetroPie/roms/mame/cfg
nvram_directory /home/pi/RetroPie/roms/mame/nvram
input_directory /home/pi/RetroPie/roms/mame/inp
state_directory /home/pi/RetroPie/roms/mame/sta
snapshot_directory /home/pi/RetroPie/roms/mame/snap
diff_directory /home/pi/RetroPie/roms/mame/diff
comment_directory /home/pi/RetroPie/roms/mame/comments
skip_gameinfo 1
plugin hiscore
samplerate 44100
video accel
cheatpath /home/pi/RetroPie/roms/mame/cheat
cheat 1

6 - Now, you can create separated systems and put all your MAME Artwork site 1, MAME Artwork site 2 in the same folder. This folder is the same for lr-mess.
/home/pi/RetroPie/BIOS/mame/artwork (you have to create artwork folder)

7 - Now, you have to create your systems (Note: mame = mame and mame-autoframeskip = mame with autoframeskip by default):

For:
/opt/retropie/configs/all_in1
/opt/retropie/configs/konamih
/opt/retropie/configs/tigerh
/opt/retropie/configs/tigerrz
/opt/retropie/configs/jakks

With MAME standalone, we don't need retroarch.cfg

emulators.cfg

mame = "/opt/retropie/emulators/mame/mame %BASENAME%"
mame-autoframeskip = "/opt/retropie/emulators/mame/mame -autoframeskip %BASENAME%"
default = "mame-autoframeskip"

For:
/opt/retropie/configs/classich

emulators.cfg

lr-gw = "/opt/retropie/emulators/retroarch/bin/retroarch -L /opt/retropie/libretrocores/lr-gw/gw_libretro.so --config /opt/retropie/configs/classich/retroarch.cfg %ROM%"
mame = "/opt/retropie/emulators/mame/mame %BASENAME%"
mame-autoframeskip = "/opt/retropie/emulators/mame/mame -autoframeskip %BASENAME%"
default = "lr-gw"

retroarch.cfg

# Settings made here will only override settings in the global retroarch.cfg if placed above the #include line

input_remapping_directory = "/opt/retropie/configs/classich/"

#include "/opt/retropie/configs/all/retroarch.cfg"

For:
/opt/retropie/configs/gameandwatch
emulators.cfg

lr-gw = "/opt/retropie/emulators/retroarch/bin/retroarch -L /opt/retropie/libretrocores/lr-gw/gw_libretro.so --config /opt/retropie/configs/gameandwatch/retroarch.cfg %ROM%"
mame = "/opt/retropie/emulators/mame/mame %BASENAME%"
mame-autoframeskip = "/opt/retropie/emulators/mame/mame -autoframeskip %BASENAME%"
default = "mame-autoframeskip"

retroarch.cfg

# Settings made here will only override settings in the global retroarch.cfg if placed above the #include line

input_remapping_directory = "/opt/retropie/configs/gameandwatch/"

#include "/opt/retropie/configs/all/retroarch.cfg"

8 - Add the following lines in platforms.cfg
/opt/retropie/configs/all

tigerh_exts=".7z .cue .fba .iso .zip .cdi .chd .gdi .sh"
tigerh_fullname="Tiger Handheld Electronics"

tigerrz_exts=".7z .cue .fba .iso .zip .cdi .chd .gdi .sh"
tigerrz_fullname="Tiger R-Zone"

jakks_exts=".7z .cue .fba .iso .zip .cdi .chd .gdi .sh"
jakks_fullname="JAKKS Pacific TV Games"

konamih_exts=".7z .cue .fba .iso .zip .cdi .chd .gdi .sh"
konamih_fullname="Konami Handheld"

all_in1_exts=".7z .cue .fba .iso .zip .cdi .chd .gdi .sh"
all_in1_fullname="All in One Handheld and Plug and Play"

classich_exts=".mgw .7z"
classich_fullname="Classic Handheld Systems"

gameandwatch_exts=".mgw .7z"
gameandwatch_fullname="Game and Watch"

9 - Add the following lines in systems.cfg
/opt/retropie/configs/all/emulationstation
don't forget to add .7z and .zip to gameandwatch

             <system>
    <name>jakks</name>
    <fullname>JAKKS Pacific TV Games</fullname>
    <path>/home/pi/RetroPie/roms/jakks</path>
    <extension>.7z .zip</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ jakks %ROM%</command>
    <platform>jakks</platform>
    <theme>jakks</theme>
  </system>
      <system>
    <name>gameandwatch</name>
    <fullname>Game and Watch</fullname>
    <path>/home/pi/RetroPie/roms/gameandwatch</path>
    <extension>.mgw .MGW .7z .zip</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ gameandwatch %ROM%</command>
    <platform>gameandwatch</platform>
    <theme>gameandwatch</theme>
  </system>
        <system>
    <name>classich</name>
    <fullname>Classic Handheld Systems</fullname>
    <path>/home/pi/RetroPie/roms/classich</path>
    <extension>.mgw .MGW .7z .zip</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ classich %ROM%</command>
    <platform>classich</platform>
    <theme>classich</theme>
  </system>
       <system>
    <name>konamih</name>
    <fullname>Konami Handheld</fullname>
    <path>/home/pi/RetroPie/roms/konamih</path>
    <extension>.fba .zip .FBA .ZIP .cue .CUE .7z</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ konamih %ROM%</command>
    <platform>konamih</platform>
    <theme>konamih</theme>
  </system>
     <system>
    <name>tigerh</name>
    <fullname>Tiger Handheld Electronics</fullname>
    <path>/home/pi/RetroPie/roms/tigerh</path>
    <extension>.fba .zip .FBA .ZIP .cue .CUE .7z</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ tigerh %ROM%</command>
    <platform>tigerh</platform>
    <theme>tigerh</theme>
  </system>
       <system>
    <name>tigerrz</name>
    <fullname>Tiger R-Zone</fullname>
    <path>/home/pi/RetroPie/roms/tigerrz</path>
    <extension>.fba .zip .FBA .ZIP .cue .CUE .7z</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ tigerrz %ROM%</command>
    <platform>tigerrz</platform>
    <theme>tigerrz</theme>
  </system>
        <system>
    <name>all_in1</name>
    <fullname>All in One Handheld and Plug and Play</fullname>
    <path>/home/pi/RetroPie/roms/all_in1</path>
    <extension>.7z .cue .fba .iso .zip .cdi .chd .gdi .sh</extension>
    <command>/opt/retropie/supplementary/runcommand/runcommand.sh 0 _SYS_ all_in1 %ROM%</command>
    <platform>all_in1</platform>
    <theme>all_in1</theme>
  </system>

10- The way I configured the controllers avoids using the keyboard. You just have to use it on the first start.

Now we load a game

• Connect your keyboard and press TAB

• You'll see this :
  

• Go in (input general) and User interface and set the following keys. It will set your controller for MAME menu.
  
  
  
  
  
  Now you can go in the menu, do your game setup and exit without keyboard. This is the only time you will have to configure the main menu options.

11- Go back in the main menu. Set your controller for your game (go in input this machine)


You will have to set It once per game because all games have different button configurations.

12 - IMPORTANT (for LCD systems and more ) : By default, they run at 33 FPS. Frameskip must be set at : Auto (set it with F8 and F9). Those games didn't have a big number of images per second on there original format, so frameskip = Auto doesn't affect the playability and recreate the real gaming experience. (Right analogue down and left thumb) It's also good for the other systems like Jakks and All in One. NEW EDIT : Now, AutoFrameskip is set by default, use mame-autoframeskip emulator/system for that.

Frameskip = auto (help sometime with sound issues)

13 - To exit the emulator or go back in the menu, press Right Thumb = escape (cancel) button

14 - Scrape systems. Not supported by sites like Screen Scraper or others at this time. See https://drive.google.com/drive/folders/1bfuYF7Ij_dhNc9b8bVCS6I22XiEmP7rv?usp=sharing for pre-compiled gamelists/downloaded_images or See site like EmuMovie (right menu - subcategories) for now and do It manually . NEW EDIT: You can use Development of module-script generator for lr-mess, lr-mame and mame standalone to do that (Highly recommended)

Tip: For Tiger games, they don't have the Screen Focus option. To have a full screen with background, go in video option and change View Full by View Cropped

15 - You are All set (for the list of games, see post #2 of this thread)

you can also read
https://retropie.org.uk/forum/topic/28182/lr-mame-20xy-and-handheld-games/16?_=1605029025333

HERE'S A THEME COVERING THOSE NEW SYSTEMS Cygnus - Blue flames

Hope this will be useful