Was this ever resolved?
Viewing post in [Answered] Extreme IDE Lag (GMS2)
"As far as I'm aware, the only thing in GMLive that can cause IDE lag is if your code is constantly throwing up errors and they are piling up in Output tab until they eventually "clog" it due to there being too many lines."
If I recall correctly this was the issue. The extension would try to connect to the server but it would keep failing and throwing errors.