When I set the Hotlist window to "carry forward unfinished tasks", any change to a hotlist task takes 15 (!) seconds to be accepted. It seems as if the entire database refreshes when unfinished tasks have been checked in the custom hotlist filter. This is brutally slow. Any ideas on why and how to fix it?

It's just a function of processing speed/memory - no different than any other application. There are "tweaks" one can do to Pervasive but most don't recommend changing the defaults. Consider first upgrading your memory and so on - you'll get increased performance all around.

IRIS