You can edit the mask gesturally and by modifying the settings in Gmask tabs. Editing operations, such as adding and removing vertices, can be effected whether or not the mask is completed. You can also edit mask properties, move vertices and tangents, add and edit the gradient, track the mask, and change display properties before mask completion.
To delete points from the mask:
If the vertex is in a mask that is a closed shape, the splines that connected it to adjacent vertices will be replaced by a single spline.