I must admit, after using GMS2 only for more than a year now, I can safely say I will never get used to it. My biggest issue is the chains - they take up way too much space for no reason, and there's absolutely no reason for restricting the modularity of the object windows. I also really wish that I could close the main "object" window (the one that contains object name, sprite, physics etc.) and just have events list and code. But if I close it, the whole entire chain closes, and I see absolutely no reason to enforce this behavior - why force windows on me that I don't need?
Also, I cannot drag a resource to another monitor without having the entire application wrap-around-border go with it, once again, taking up way more screen space than necessary. In GMS1 the window was self-contained. Come to think of it, in spite of its issues, the GUI in general was way more compact. Everything in GMS2 just takes up so much space on the screen. More than it needs to.
Another thing - yes, I may be able to overlap windows with a setting (which I use, otherwise I would go crazy), but that still doesn't change the fact that everything is literally chained together. Also, those completely unnecessary vertical "drag lines" at each side of a chain's window will overlap other things, like a code editor below. I wish I could remove those altogether. Why not just let the user drag by using the edge of the window like everywhere else? Those vertical lines are once again completely unnecessary and take up space and get in the way (seeing a pattern here).
There are some very good things about GMS2's IDE GUI too, but I've actually come to find that I worked much faster in GMS1. The workflow was just faster for me. And so much more compact. This isn't just a preference, this is a measureable fact - everything takes longer for me to do now, due to a worse workflow.
Removing the forced chaining would be a great first step in improving the workflow. Can we at least please consider that?