Where do I find the staff properties?

The staff properties were moved with the release of FORTE 11 in 2019.

If you want to change the instrument, the staff's appearance (Drum Staff, Tablature, Grand Piano) or the performance qualitites, this is how you get there:

Method 1:

Switch to select mode using CTRL+1.
Single click the lines of the desired track.
Right click and select "Select Staff (Track)".
The properties window opens.
You can edit the element now.

Method 2:
Open the mixer, using ALT+3 OR clicking the mixer icon on the main menu.
Double click the name of the desired track in the mixe.
The properties window opens.
You can edit the element now.

If you use FORTE 10 or earlier versions, double click the track to open the staff properties.