My suggestion today may be of greater interest to power users, but I'd like to see a greater ability to edit single items within Opera -- in this case, to remove the display of individual items from the Downloads list, rather than clearing out the entire list in one go. I fondly recall having this pinpoint control over almost everything in legacy (5290) FireFox, which I still make some use of occasionally, even though it is supposedly very outdated.
I recently had a nearly disastrous outcome due to following the advice of AT&T Tech Support, a mistake that I won't make again. I had gotten temporarily locked out of my email accounts, with repeated, circular Login failures. (This happens from time to time, and is entirely caused by faults in their system.) Their advice was a standard one: first, clear the Cache & Cookies. However, their advice for doing this in Opera deleted not only all of that but also other things like the entire browsing History -- which I really wanted to retain for reference and the ability to retrace my steps for certain sites I had visited. That indeed proved to be "throwing out the baby with the bathwater." I managed to recover or reproduce some of what was lost in this process, but not the History. In the aforementioned Legacy FireFox, I had long had the ability to delete individual History items, edit or delete individual Cookies or groups of them, as well as individual items that would show in the Downloads list, without disturbing other items. You could put that degree of control somewhere under 'Advanced' Settings, leaving it for users seeking such more detailed options, without it getting in other user's way.
Fortunately, I have found and begun to explore some Opera extensions, including Cache Cleaner, Cookie Cleaner, and Cookie-Editor, which provide some of these controls. I've learned that individual History items can be deleted in Opera, in a straightforward manner. Still nothing for editing the Download List, though.
Another thing I really miss from the older FireFox was the ability to backup one's entire Profile, rather quickly and easily.