Okay, as a matter of background, I'm using Kubuntu 16.04 which, as best I understand it, uses KDE 5.4. So far I've either figured out how to fix all my post install issues and tweaks, save only for three. So I'm wondering if you guys can help me sort these out too. Here's my list.

1. In the taskbar, the application tabs seem sorta crushed together vertically. I'd like to make them taller. Now, as a point of note, I'm using the Oxygen theme rather than Breeze as I like it better. I don't have the tab problem in Breeze. Just Oxygen.
2. Inversely I'd like to also make the couple of icon shortcuts I have in the taskbar (show desktop and konsole) larger than they are. Not much larger, but at least a little bigger so they're easier to see.
3. On the taskbar I'd like to have some kind of clear difference between regular and minimized windows the way it was in KDE4.x. Right now you can't tell what's minimized and what's not.

Anyhow, any help on this would be much appreciated. Thanks.

1. In the taskbar, the application tabs seem sorta crushed together vertically. I'd like to make them taller. Now, as a point of note, I'm using the Oxygen theme rather than Breeze as I like it better. I don't have the tab problem in Breeze. Just Oxygen.
2. Inversely I'd like to also make the couple of icon shortcuts I have in the taskbar (show desktop and konsole) larger than they are. Not much larger, but at least a little bigger so they're easier to see.
3. On the taskbar I'd like to have some kind of clear difference between regular and minimized windows the way it was in KDE4.x. Right now you can't tell what's minimized and what's not.

1. I am not having this issue on either Breeze Dark or Oxygen (though I'm on neon, which uses 5.9). To resize the panel itself, right click on the panel -> click panel options -> panel settings -> drag on "Height."
2. As far as I know, widget/applet height is determined by the height of the panel. See above for how to resize the panel itself.
3. I'm not sure but I think that if you right click on the window list, then click "Task Manager Settings" and enable "Highlight windows" from there, then it will differentiate between overlapped, minimized, and focused windows.
Hope I helped,
Ivan

Okay, thanks on #1 and 2. As for 3, it does highlight the active window, but you can't tell if non-active windows are raised or minimized. That's my biggest issue. I do though have the highlighting on already, so that helps some.

I use KDE 5.9 and it highlights minimized windows in light gray. This seems to be an issue with Kubuntu or its KDE 5.4 desktop. You should upgrade KDE by either:
1. waiting
2. adding the Kubuntu backport repository (ppa:kubuntu-ppa/backports), which includes KDE 5.8.

Hmm, okay, so if there's big improvements in KDE now seen in 5.4, but available in 5.9, then yeah, that might be the better way for me to go then.

Okay, I ran the update and it seems to have solved the crushed taskbar tabs problem. Icons are still too small, but I can live with that. Not sure what version of KDE I'm on, but I did see a bunch of improvements. Any way I can easily tell what version I'm running?

EDIT: Found it. I totally forgot about using Infocenter for that. haha. It says I'm on Plasma 5.8.5 and 5.28 for the framework.