Right in the toolbar popup offers a "..." button with an "exclude" menu item, for the current domain:
Also has a settings tab under the script editor:
With six different boxes, three display the script's include/match/exclude values, with (checked by default) "Original" checkboxes that can turn off these values, and "user" include/match/exclude" boxes, which each have an add/edit/remove button. There's helper buttons for coping the script values into a particular user value each.
I want to add at least a "+" of the current domain, like exists for global excludes already, before calling this done. As always, testing of the next nightly build ( http://arantius.com/misc/gm-nightly/ ) including these is greatly appreciated!