Sculpt: Mask Slice
This operator is similar to Mask Extract, but it deletes the masked points on the original mesh and fills the holes. This can be useful for quickly trimming or splitting an object.
This is not meant to be the main trimming tool of sculpt mode. I plan to have a set of trimming tools based on geometry booleans (trim box, lasso, line, bisect...) but in some cases doing a mask selection is more convenient.