For sure. The Synthetik dev team (a German duo) I recalled did extensive modifying of Game Maker Studio to suit their needs. GMS really wasn't intended for online co-op but they managed to make it work reasonably well for 2-player online co-op although it was probably never as reliable as they wanted.
They if I recall moved to Unity for the sequel - which has been in Early Access almost 4 years now - and while it's more robust I suspect it brings its own challenges.