The easiest way to test this is to load a session that restores multiple documents op launch, and open the "menu allowing to stop individual jobs". Or click the "Revert all open documents" toolbar button (which really should be called "reload"! ;)) and then open the run controller menu. Keep it open, the document count is updated. Click the entry to stop background processing (= cancel all pending parse jobs - cancelling the current job cannot be done safely it seems).