Same problem here. Project worked last time I ran it. Now it freezes if I try to save or add variable to level blueprint. I tried the “Fix redirectors” on my content folder, and then it removed my map… 
Specs: AMD Ryzen 9 5900X, NVIDIA RTX 3080 Ti and 64GB of memory. Nothing peaks or anything.
Alright, I seem to have found out what caused my issue. I had two paragon characters and I tried to merge them together (share the Global folder instead of having a seperate for each character due to alot of duplicates), by doing “Replace reference” from one character to another. Reverting these changes brought my project back. So it’s probably something with material instances/master materials as stated above.