Constrain Direction

I’m trying to find a tool modifier keystroke to make constrain direction work properly in the arrange page (on a Mac), so that vertical drag & drop keeps events in the same place on the timeline.
I’ve managed to assign a key command for nudge up & down, but would also like to find a way of doing it using the mouse.
Does anyone have a solution? (The default tool modifier, Command is not working for me)

Cmd and Control.

Cmd really should be working. Please be aware that, when using modifier keys (and, especially, key combinations) while dragging, what matters is which keys are still held while the mousebutton is released. You can even press the modifier keys after you have started to drag the event… it shouldn’t matter, so long as they are still held when releasing the mousbutton.

Ah thank you both of you - pressing command and control after dragging but before releasing mouse is working