You've got to stop sneaking things in on me. I'm old, and easily startled. If I fall off my desk chair, you'll be responsible for the consequences.
Just did a quick test, and that works nicely. I chose square-cropped folder and regular thumbnails, but chose one crop focus for the folder thumb, and a
different focus for the same image
within the folder. Looks solid.
And it looks like
Make album is picking up a change to the crop focus on the folder thumbnail without any need to force the issue.
A mask in the
Thumbnail box would be the icing on the cake, so I'll leave this thread open for now.