Hi Richard,
great to hear, I've also seen a tweet about new videos from you using VS code (had no time to watch yet).
Hope that more adoption improves things!
So, I've been using VS Code for almost a year now and I have seen great improvements - almost all of that is the Haskell LSP.
"processing" and "indexing" may be (at least the former?) the LSP, I guess? I have head single instances where it went haywire and I had to do a hard reset of my machine,
but generally I can work with VS code and LSP doing it's thing (Laptop with Ryzen 4700U & 16 GB RAM).
You can hit Ctrl+Shift+P for the command HUD and type "Haskell" - this gives you the options to stop and (re-)start the LSP.
The latter can help when it becomes sluggish.
In File -> Preferences -> Settings search for "Haskell", there you have the option to turn off things, e.g., "Haskell: Diagnostics on Change" (turning off will create diagnostics only when you save).
Hope that helps.
Cheers,
Ben