Updated: March 29, 2023
GwenView is the default image viewer - and sort of image manipulation - program in Dolphin. It's pretty decent. But in Kubuntu 22.04, the way it's configured by default, as I've explained it in my Slimbook Titan review, the usability is subpar. You have no menu, no buttons for quick actions. But Plasma is awesome, and you can customize things as much as you need or like. So, I quickly remedied the initial shortcomings. I added a menu, I added a bunch of buttons to the toolbar, disabled video view, added checkered background to images with transparency, and changed shortcuts for quicker action and work, like Esc for exit, s for save, c for crop, and similar.
The one thing I wasn't able to instantly fix is the sidebar. The stuff there is simply too small. The interface obeys my HD scaling all right, so there isn't an issue there, but for some reason, the folder contents, image details or image manipulation operations listed on the left side are rendered in tiny font. The text is too small to comfortably "see", and there isn't a toggle/option anywhere in GwenView's menu. OK, let's rectify that.
You can't change it in GwenView, you need Settings > Fonts
As you can see above, I made GwenView so much nicer. In the default view, there's almost nothing there. No menu, home button. Only View/Browse, Share, that's it. Not cool. For me, the important quick actions are crop, copy, resize, so I added those. You want to know when images have a alpha channel? Boom. Still, the tiny font annoys me a lot. It might not look like an issue right now on your screen, but it is a problem when you use a 15.6-inch laptop with 2560x1440px resolution (even with 125% scaling).
OK, the solution is to either hack the GwenView configuration, which we do not want, OR to change the Small font settings in Plasma's Settings menu. Basically, Settings > Appearance > Fonts. Change from whatever the default value is, something like Noto Sans 8pt, to a much higher value. Like 11pt.
And that's it. Now your UI will look awesome:
We went from this:
I understand there's a need for some sort of visual hierarchy here and there. That can be achieved by making the title Image Operation bold or semi-bold. Perhaps use a wee larger or smaller font, but the "small" one just isn't the right size, especially not for essential functions. That can work for hints or less important details, surely not for image operations that are, by all measures, equal to everything else in the UI. Also, this makes the GwenView inconsistent, because some KDE programs do let you change the UI font sizes.
Anyway, despite the problem we had at hand, the Plasma desktop once again proves its superb customization. Even if you really dislike something, there's often, almost always an easy way to fix it. My Kubuntu is "stuck" with the LTS release (which has no, for instance, resizable main menu), and some new features and options are only available in later Plasma editions, but even so, there's a lot of goodies available, and no need to resort to command line, QML or CSS tricks. Quite alright. Time to say bye bye, and your GwenView is now both pretty and functional. Peace, fellow penguins.