In Bongos, all buttons are locked by default. You can move a button by either by first holding down the quick move key (control by default), or unlocking button positions.

Button positions can be unlocked via the options menu, which can be triggered by /bg if its enabled, or via the slash command /bg unlockbuttons.

If you're using the Nurfed UI, there's an option to lock button positions in it. Make sure its turned off, or else it will not be possible to move the action buttons.