In Boost, it became quite difficult to find how to "Turn editing on". It was already a bit problematic in Clean as I don't think users clearly understand that the editing mode from the course page has an effect on the other pages, but with Boost that makes it even less clear.

I discovered this while testing MDLQA-9923. To add blocks during a quiz preview, I had to go back to the course, expand the dropdown menu and turn editing on. Then head back to the quiz, expand the drawer and find "Add a block" at the bottom.

This is quite a "travel" to get to turn on editing mode. Previously you could "Turn editing on" from the "Course administration" node in the "Adminstration" block, without changing page.

Another UX issue may be that users will not understand when "Add a block" appears on the page. That may have been an issue before but I find it more confusing now that "Add a block" is a link like all others in the drawer.