I'm a bit confused by this discussion.
The Tag Browser panel, where the Collapse All button is located, can be re-sized by the user with the position of all elements redrawn accordingly. The only time that this button might "stick out" is if your listing has extremely short terms.
If I want to see a wider Book List, I have to either temporarily or permanently:
- turn off the Tag Browser (or Show Book Details)
- narrow the width of the Tag Browser (or Show Book Details)
- obtain a higher resolution monitor
Since the monitor isn't an option, that means I have to regularly alter what calibre displays.
You have the same options, so what is the problem with switching things around as needed?