[john.gersh]

Depends on what you mean by "turn off." You can't make a shared layer invisible for only one canvas. You can delete the shared layer from a canvas. Select it and hit delete or right-click and pick "Delete Layer." For a shared layer there are two right-click choices - "Delete Layer" [from that canvas] and "Delete All Copies" [from all canvases].

If you want to restore the shared layer to that canvas at some later time, just drag it to the canvas from another canvas that includes it.