is there a way to add handles to the rotoscope mask i've created? Or, once created, the handles are set.

I've found that there are times I need to adjust the mask more intricately, say, 50 frames downstream, and don't have enough handles.

When you have finished and closed the mask and you zoom into the monitor view you can see on each site of the square mask points some small points. That’s the bezier handle you can adjust.