Hi
"PS. What keyboard shortcut to mute the selection? "
It doesn't need a keyboard shortcut... This is the procedure to mute a section of a clip on the timeline.
With your clip on the timeline, move the red cursor line to the start of your section to mute. You can play it to this point or drag it or refer to the audio peaks. Use Split audio track. (Or you can split all tracks if you want)
Move the red cursor line to the end of your section to mute. You can play it to this point or drag it or refer to the audio peaks. Use Split audio track. (Or you can split all tracks if you want)
Right click the section of the audio track to mute and select "Mute Audio"...Job done! :mellow:
Nat