@Zeblote](CPU utilization - Feedback for Unreal Engine team - Unreal Engine Forums) I see. There is a bug in Chrome/Stylish iframe injection.
This issue is only fixed in Stylus addon.
I’ve added minor tweak to make it less painful in case you don’t want to change addon. You have to switch editor to “source view” and back and it should apply the style.
I’ve added to theme all(I think) the CKE popups.