You may also try the scriptmodules I put together a while ago, but do still work fine. These make ScummVM game setup and switching between ScummVM and the lr-scummvm a breeze.

https://retropie.org.uk/forum/post/275199

With that branch you just have to have a file structure like this in the ~/RetroPie/roms/scummvm/ folder:

... ├── Monkey-Island-1 The-Secret-of-Monkey-Island/ ├── Monkey-Island-1 The-Secret-of-Monkey-Island.svm ├── Monkey-Island-2 LeChucks-Revenge/ ├── Monkey-Island-2 LeChucks-Revenge.svm ...

The actual folder name and .svm filename do not matter per game, they just need to be matching per game like above. The *.svm can also be empty initially, the game id will be filled in by my scripts. Just put the required game files into the respective game folder as per ScummVM wiki.

Start a game with the native ScummVM once, then you may switch at the second launch to the libretro ScummVM in the runcommand menu. And switch back and forth. That's it, that's all. :)