I also use HDD for my projects, and 4.3 works perfectly fine with that.
Upon testing it again, disabling the Plugin Studio Telemetry has resolved the lag issue. Additionally, disabling TCP and UDP also seems to provide some additional improvement. However, it raises the question of why these actions slow down the Editor. Is the excessive ping for sending user data causing this issue, or is it a bug? This is not a new issue; it has been mentioned before as a potential solution for fixing a laggy Unreal Editor. However, this does not seem to be a problem in Unreal 4.3 for me. Is it related to the telemetry plugin or is it a new bug related to TCP/UDP messaging?
Can someone please help confirm my discovery or explain what the telemetry plugin is for?
Thanks in advance!
Edit: I enabled the telemetry plugin again and noticed that when starting PIE, it was running at a very low FPS and I was experiencing extreme lag, just like what you mentioned.