I don't understand why the list isn't full page length, or paginated, and why it is scrollable inside the html area. I mean, we all have scrollbars in our browser, embedding scrollbars inside scrollable windows seems redundant to me.
Or stuff like this, opening a modal with scrollbars horizontal and vertical. If the information doesn't fit in a modal, maybe a modal isn't the best way to display it.
Don't take this the wrong way, I want XF to be great, but the admin panel feels a bit counter-intuitive at times and I think it's something that could be improved at low cost (in time and resources) but have a big impact on users and potential buyers.