I saw you can mute the bar using F5 and then Vol Changes/All/Mute.

But how do you mute just beats 1 and 2 of a 4/4 bar?

So bar 1 (mute)
Bar 2, mute beats beat 1 and 2.

Also I would like to have a shot in bar three like this:
Bar two, beat three chord Em7,
Bar three, just BEFORE the beat, shot chord A7.

TIA!

I think this is what you want:
Place a rest on the first bar by following the Chord with a single Period.
Place a rest on the first beat of the 2nd bar and a normal chord on Beat 3 of Bar 2

On Bar three, place Em on the 3rd beat the bar followed by a push for the A7 by using a caret character

C. |C. C | Em,^A7 |

Thanks very much VT!
It actually worked.

I didn't use the ^A7, as I hadn't seen your edit.
But will try it later to see if it improves the results.

Excellent. Glad to be able to lend some assistance. Thanks for the feedback.

Video Track gave you the shortcut method. You can make changes by R-click on any bar and then select Chord Settings, as well as F5.

You can use the edit box that opens and go from there. You can also make other changes with the Bar Settings feature as well.

Trax