Danoise gives some excellent advice in this thread: https://forum.renoise.com/t/renoise-tools-speed-optimization-initiative/45510
If you have a specific example of something heavy, I’m quite sure you could get some help on the forum by posting an example.
PS. Being on an i7 processor, I’ve only really noticed heavy load during one specific circumstance - when heavily swapping the positions of large instruments. I’m curious if even this could somehow be “masked” with idle notifier and possibly coroutines.