The VideoLAN Forums

Ah I found it. It is draggable from the side edges, not from any corners. And it is hard to discover because the mouse pointer does not change into the standard horizontal arrows when positioned over the region that allows it to be moved.

The panel is not draggable to resize, only to move.

I used to be able to make the play controls stretch across the entire bottom of the window in fullscreen mode (though it's possible this was on a PC). I cannot for the life of me find any option to do this in the current mac version. Having it be so small makes scrubbing very imprecise.