Select the mask layer you want to delete in the Canvas Layer Editor.
Do one of the following:
Choose Delete > Painting > Delete Active Image Layer .
In the Canvas Layer Editor window choose Edit > Delete Active Layer.
The active mask layer is deleted.
Select the canvas plane in the Construction Plane Editor.
If you can see the mask layers that you want to delete in the Canvas Layer Editor, then the canvas is already selected.
Choose Delete > Painting > Delete All Mask Layers .