Inconsistent mouse behaviour

Middle and right mouse buttons behave differently in the three edit modes (song, beat and piano roll).

The double click to open (or step into) is also quite confusing as it sometimes also inserts (or toggles) what you point at.

I suggest to either (or both :)

• Have the hint window explain what the different mouse presses could do (whenever the mouse is over something it could interact with).
• Make the mouse buttons behave more consistently :D

Ideas to make mouse behavior more consistently:

• Middle mouse button: delete/unset selected.

• Right mouse button: open context menu (if any) (*)

• Disable using double click altogether (to open something instead use right click and select the top option).

  (*) This could also simplify the track headers in the song editor. The Cog symbol could be removed, as a right click would open the menu instead. Rename should be added to the menu.

Compare mouse handling across the song, beat, and piano roll edit modes, starting with the existing hint window and track-header interactions described in the issue. Determine whether the intended outcome is clearer hints, consistent button behavior, or both; done means the chosen behavior is consistent and double-click insertion or toggling is no longer confusing.