I don't use it normally, but doing a test now with current fixes branch (that is newer than 4.2, but not too much) shows it works. (And my fixes currently even has anchor dock installed, and I had 2 source editors open / in 2 separate docking windows)
Obviously, the options need to say "update on idle". If you have "manual" or "never" then it wont happen.
And mind, IDLE is not immediately. It feels like it takes about 1 second before it follows.
And if you have something that keeps the IDE busy, then it wont update (e.g. during compilation / not tested, but seen in other similar handlers). Same if you have a rogue package, that keeps the IDE busy forever.