Its so frustrating, every time I log into Relume it's incredibly slow, laggy, I'm starting to think I should move away from this tool as it wasn't like this when I first started using it, things barely work ever
Zlatko M. incognito won't remove extensions - you'd have to go into guest profile to test if its an extension. Do this and let me know what you find.
https://support.google.com/chrome/answer/6130773?hl=en&co=GENIE.Platform%3DDesktop
Another thing would be to split pages across many sitemaps - more time-consuming, but it sounds like speeding up the canvas would be more important to you at this point.