Great! Thanks a lot sgunhouse and RoadHazard!
I feel stupid now for this, but I had completely missed this "Flags" page before. I was so disappointed at first that, while continuing to use 12.x for regular browsing, I didn't read enough of the new versions' fine print nor did I played around enough to explore. When I couldn't find any "opera:config" or satisfactory "advanced" settings, I gave up too quickly and simply assumed there weren't as yet easily configurable options beyond Ctrl+F /main menu settings. But now, the mere knowledge that there are already quite a few not so obvious options to fiddle around with has improved my Opera-related mood by more than just a little. Quite a bit, actually. Knowing that features like this are slowly coming back gives me hope that other, sorely missed, former Opera features may follow suit - if not today or tomorrow than perhaps the day after or, if not then, than at least at *some* point in the future. As long as it is sooner than "never", I know I'll be happy - in the end.
I'm still wary/doubtful about Opera's future and whether it will be able to find and reclaim its former character, that special uniqueness that so many among us simply can't conceive of doing without. But there's hope, and the info I've received here has now improved mine quite substantially. Development may appear to be proceeding at a snail's pace, but the task of migrating Opera's defining features to the new engine, presumably, has hurdles and challenges on its way that can't be bypassed and require substantial amounts of time. But I remembered an old saying, though not the exact words of it: "The slowest growing timber gives the best wood". The first part, about growth that's slow, applies to Opera's transformation into a Chromium-type browser, no doubt. I sincerely hope the second part of the saying, about the quality of such slow growth will, eventually, apply as well. Pressing both thumbs.
I'm very grateful you guys got me up to speed here. This helped me in more ways than expected. Thanks.