I'd rather have Hot Network Questions removed, as instead of reading a SO answer I need I always end up distracted by "How would a sea turtle end up on its back?" kind of questions on the right side
If you have never used that feature, it's great! It allows you to visually pick and hide unwanted blocks, like say, the Youtube sidebar. To unhide the blocks you can go to the main icon of uB and at the bottom of the menu you have "toggle cosmetic filtering for this site". To remove that specific filter entirely, you can go to uB main dashboard > My filters.