Insert/remove bar buttons in Song Editor

[allejok96]

Seems like back in 2006 the insert/remove bar buttons was removed from song editor, keeping only the keyboard shortcut shift+insert. I just recently learned about this useful feature. Like pointed out in #5599 having keyboard-only features is not user friendly, due to lack of discoverability.

Why not bring back these buttons? This should be a very easy task, since the feature exists.

Would also be nice if this feature came to piano roll, but that would require a little more work I guess.

[PhysSong]

Hi! If you have ability to put it back, that will be great. Otherwise, someone else who looks for easy tasks can probably do this.