If you’re working on editor stuff for Unity 2019.1 (or up) you’ll probably want to use UIElements instead of IMGUI.

I’ve been working on replacing IMGUI with UIElements for my own plugin RetroKit and so far it’s been a huge improvement in terms of performance, code quality and my happiness when working on the UI. 🙂

I made a short list of Unity documentation pages (mostly) that I found most useful (so far):

• Developers guide (good place to get started)
• Code examples
• Overview of elements
• Overview of events
• Overview of supported stylesheet properties
• How-to define your own elements
• Video tutorial (about the 2018.3 version, so some information might be out-of-date)
• In Unity 2019.2, you can check the UIElements Sample Window under: Window > UI > UIElements Samples (Thread about it here)