Let’s see what’s wrong with this UI here:
1. No action button unless something is selected. You won’t be able to press it but it’s good to have it visible anyways to plan your actions.
2. Selecting first item pushes the whole UI down. It’s better if UI content doesn’t move.
3. The primary goal of this UI is to free up some space. Yet it doesn’t show you how much space will be freed.
4. Selecting an item hides its details, in particular, its size.
5. Fourth column has a header that says “Size” yet it displays items.
6. Action button appears at the top, before the content, which is unusual for desktop UIs.
7. If you scroll down you see no action button.
8. Primary action button is an icon with no tooltip. For such an important action (Permanently delete) it’s better to use text label and red color.
9. You expect X button next to “2 selected” to clear the selection, but it closes the whole UI instead
Thanks Akiva Gordon for reporting this