As demonstration: MIDI editing functions and scripts that follow mouse movement can be linked to toolbar buttons, armed by right-clicking, and then executed -- but only in the piano roll area:
This very useful feature does not work in the controller lanes.
The GIF also demonstrates a related bug:
When a toolbar button is armed, left-clicking should *only* execute the armed function -- not the left-click mouse modifier action. In the GIF, left-clicking also runs the "View: Move edit cursor to mouse cursor", which I have linked to the left-click default action.