I slide the screwdriver in from the other end (where the red circle is) and push the scredriver handle towards the wiring and this JUST lifts the tab enough to release it.
But push the plug IN first or the tag will be held firm.
I cut the tab off, and they just pull off now. Never had one fall off, and they still seal fine. Very poor design of connector, I'd say SAAB ones are the best I've ever used.