In the References dialog we can create a Clip Volume and a Clip Mask for several selected References in the list.

Moreover there is a "Delete Clip" button which is enabled when the selected Reference has applied a Clip Volume or a Clip Mask (or both)

So the same button is for removing a Clip Volume or a Clip Mask.

In my opinion, in the datatable of References should have 2 new boolean columns (Yes/No readOnly) as information such as "Has a Clip Volume" and "Has a Clip Mask" to know if a selected Reference has one of them or both.

Even we could click on the cell to highlight the frame/s of the Clip Mask.

Or having 2 buttons: "Delete Clip Volume" and "Delete Clip Mask" separatelly.