Well, the older thread here that I already mentioned (in post further above) is discussing something even more difficult, i.e. stopping a dur: inf event with stop… My clock-acceleration solution won’t work for that, only the/your group-based solution works for that. By the way, I’ve posted a fairly simple Pproto wrapper for that over there, but it has the caveat of not gating out but killing the group (I think).
One way to fix/enhance this would be for the Clock to expose more its scheduler, i.e. have a “lookup and reschedule” function. In some priority queue implementations (not SC’s as far as I can tell), there’s a primitive to change the priory of an event/item already queued. (With the usual min-heap-based implementation of priority queue, only moving events closer to “now” is allowed.)