For others that finds this thread hoping to solve stuttering in Unreal Engine Editor, go to your Project Settings → Plugins → UDP Messaging → EnableTransport (Set this to false).
This solved it for me, I had the Editor FPS drop happen in 4.27, 5.0 and 5.1, no content browser up, empty scene and no blueprint windows up.
PC specs: 3080Ti, 128GB ram, threadripper CPU (24cores) and so forth.
PS: More info, UDP is related to network settings.
If you are using a VPN that might cause this issue too.