Deletes all canvases of the selected type in the scene.
To delete one canvas
in a scene, pick the canvas in the Construction Plane Editor or
by choosing Pick > Object 
, and either press the 
key or choose Delete > Delete Active 
.
To delete all canvases of a particular type, use the Delete Canvases tool. It offers the following choice of canvases for deletion:
Choosing this option removes all canvas planes and overlay planes (planes visible only from specific view points)
Choosing this option removes all overlay planes only.
Choosing this option removes all canvas planes only.
Choosing this option will only remove overlay planes that do not have bookmarks associated with them.
