You can edit the mask in three ways: by gestural action, by using the Edit Box, or by modifying the settings in in the 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, change display properties before mask completion, and make shape transformations by enabling the Edit Box button.
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.