Is it possible to bind Win+Q key to open Total Commander or if it is already running - focus on it?
In total commander, you can set it to allow only a single copy
Configuration -> Options -> Operations -> Allow only a single copy ..., so if anything tries to open TC it will only focus on it.
You can bind a key combination to any shortcut you have in the start menu, so you can bind
Ctrl+Alt+Qto it (this is what windows does when you key in
Win+Q). If you don't mind using extra software - maybe AutoHotKey can help you (I never tried it, just found it on another post on this forum).