Any way to edit rotobrushed frames without propagating?

Hi, after doing rotobrush analysis,  after full propogation, there are times when I want to edit a frame, but not repropogate anything to left or right of that frame.  Seems whenever I do this, propp[ogation starts again.

What is the proper way to go about this? Am I instead suppsoed to render the alpha mask and edit the mask directly outside of the rotobrush editor?

thanks