i found something in Retroarch / Emustation
Hotkey + Right → Speedup game
Hotkey + Left → Rewind (if activated in options)
I haven't see it because I deactivated Rewind Option. So I thought Hotkey + Right/Left was not assigned
In Hotkey + B → Retroarch Menu : I can assign hotkeys
Input > Input Hotkey Binds
But currently I need to do this for each emulator. I don't find how to set once for all.
Also, I don't know how remove/unbind hotkey assignment, so I have 2 actions on same hotkeys (Captain, please 🙂)
Hotkey + Right → Speedup game AND Vol+
Hotkey + Left → Rewind (if activated in options) AND Vol-
I progress in my learning.