Leaving the Mylio window open seems to use a lot of CPU even if I don’t do anything with it when a sync is running. Once I minimize Mylio on my Mac OS Mojave, the CPU use goes down right away to a much lower amount and the fans slow down. Closing the Mylio window just leaving the menu icon does have the same effect.
I don’t know what exactly the Mylio UI is doing, but this even happens if I don’t have the sync panel or the activity panel open. And I just tested this with just a folder open that does for sure not get any updates right now.
Even having the sync or activity panel open I wouldn’t expect a heavy CPU use from the UI as it should not be doing extensive work to update that.