Not sure if this has been mentioned yet or if its even a real bug but if a material editor window has been open for a while, it asks to apply changes again. It's a minor inconvenience at most but when working I tend to have multiple tabs open in Unreal so when I finally decide to shut down and close a project I find I have to re-apply changes to all currently open materials. Sure, I could say no, or apply to all. I usually just apply all as a just in case which can take up to five minutes depending on how many are open. Anyway, it's just something I thought I'd mention here.