Editor and Crop Volume modules

I am using 3D Slicer version 4.6.2 to convert MRI data into a 3D representation of a head. I have two questions -

  1. When I use the “Paint Effect” in the Editor Module to fill in empty spaces and then I use “Make Model Effect” to create a new model, I cannot undo changes in the previous model. Is there any solution to this?

  2. Also, I am having issues using the Crop Volume module. I initially created an island around the head in the Editor module, which essentially built a cube around the head, and then applied that to create a new model. I am now trying to use the Crop Volume module to make the cube smaller and the program is not allowing me to do this.

Any help would be appreciated. Thanks!

It should all work well if you use latest nightly version of Slicer and the Segment Editor module (instead of the legacy Editor module).