Is it possible to delete tracks, or at least midi notes with a keyboard button?
For example the DELETE button?? Like in any other software.
I see there are some custom shortcuts, but not for the piano roll.

Welcome to the forum,
 
To delete a note in the PRV: Simply select a note, then press the Delete key.
To select a range of notes in the PRV: Right click and hold / drag=Lasso a group of notes, then press Delete.
To Delete notes in different areas in PRV: Hold CNTRL and select the notes, then press Delete.
 
To Delete a track in the Track View: Highlight the track and right click on it, Choose Delete track.
To delete multiple Tracks in the Track View: Click and drag to select a range of tracks or hold CNTRL to select multiple tracks,
then right click and choose Delete 2 tracks.
To delete only the content of the track: Click inside the Track (where the content is) and select Delete.
 
Hope this helps
 
Chuck J