I've been working in GM since 2012(GM8, Then GMS, now GMS2) and I absolutely hated the new integrated editor for GMS2. I think It's probably great for more art/DnD type people, but for coding it is, IMO, basically the least-usable thing. I totally avoided moving to GMS2 because of it's ide. 

Then, I discovered GMEdit and I'm now, fairly happily, using GMS2. The editor is fast and responsive, extendable, and (agian imo) is light-years ahead of either GMS or GMS2's editors. 

With the inclusion of builder, I only really have to use GMS2's built in editor for menial tasks and placeholder assets.