I don’t know of any “one button” command. I would say the easiest way I’ve found to do it (rather than selecting clips one by one) is to select all tracks except track 1 (lasso everything) and use the “nudge down” feature. I’m not sure what that is by default but you can search for it in keyboard layout. This ensures everything stays in sync and if you continue to do this until everything is on track 1 then you’ll be all set. I’m not sure if you do this already or if you really do grab clips one by one, but this doesn’t take that much time.