Please see my highly technical recording of this phenomenon. (Note: I finished typing the activity title, one handed, before 6 seconds into the video. Studio caught up at about 13 seconds.)
A fresh project will be fairly responsive (although there is still a slight delay behind each keystroke).
In the video recording, I had just opened Studio afresh and opened 3 relatively simply workflows. Doesn’t seem to be a system memory issue, as the rest of Studio is fine; no other performance issues to note. It is just specifically when changing the activity titles.
Does anyone else experience this? I’m on 2018.4.5 , but have seen this in earlier versions too.