Answering myself, because I'm an idiot. Sorry.
In the emulator's settings (on the GUI) I had to (re-)assign a correct mapping for pause.
It had kbd.esc and two other weird keys from the controller assigned to pause.
I assigned the button behind/below the right shoulder key to pause, no idea what those are called.
Which in my case resulted to the following in controls.ini:
[ControlMapping]
... snip ...
Pause = 1-111,10-197
Rewind = 1-67
So, 10-197 is the key that was missing.