phil_m: Windows 10, not related to Big Sur. As a test, I reverted to 3.01, and the problem largely disappeared (responsive around 500ms or so, so a bit clunky but much better).
Hi datacommando: as a forum user, you should know that there's little point in repeating other people's posts or being a d*ck about things. And I do know that when reporting an issue to include as much information as possible; and I probably would if any of the developers asked. However, before wasting my valuable time grabbing pages of specs, I'd like to see if this is a known issue. Remember, I'm evaluating this software for purchase. I'm a busy guy. If I have to spend more than 5-minutes debugging a product of a company trying to sell me a product, it's too late. They aren't going to get my business; there are too many alternatives.
And, as a software engineer who has been hacking the s*it out of computers for 30 years, I can tell this isn't related to processors or the M1 issues; it's more likely related to a lack of sensible caching. And no, that isn't a guess; I've monitored the process I/O and it appears to be repeatedly and identically accessing the disk an awful lot when ever re-trying to refresh the Edit screen (and no, my disk isn't slow; it's a top of the range SSD). Any developer on the team who reads this re: edit tab, should be able to home in on this and diagnose.
Hope this helps/makes sense.