While #168556 is still open, I have to start the IDE into the "last used" project group (folder-of-projects, around 50 maven2 projects with a decent set of dependencies, in most cases) and then switch to the project group I actually want to be working with. 

Problem, however, is that as soon as I start in the "large" project group, "scanning projects..." starts, to eventually last for about half an hour scanning maven2 artifacts of projects not really open anymore, and, as a side effect, slowing things drastically down and practically rendering code completion unusable. While in most situations one got used to long-running "scanning projects...", in this very use case a feature to stop a "project scan" altogether seems desirable, as there is no use in scanning projects (and dependencies) not even opened / in use at the moment.

https://netbeans.org/bugzilla/show_bug.cgi?id=168556