On my OpenSUSE, leap 15.4, I can do a right click on the KDE5 Desktop to pop up a menu containing "Add Panel", which pops up another menu containing
- Application Menu Bar
- Default Panel
- Default OpenSUSE Panel
- Empty Panel
Setting an "Application Menu Bar" on one edge of my screen and an "Empty Panel" on another, they look pretty similar to me and moreover I cannot figure out if there is is any difference between them regarding functionality.
Can somebody pls. explain, if/how "Application Menu Bars" and "Panels" differ and if they do, for which purpose, which of them one should use?
Thx.

A menubar is what it says, it displays the menu of the applications which you find in their windows. It's the same as global menu or system settings>startup>background services>daemon for menus (something). A regular panel is empty. But if you add the global menu widget you kinda get the same.

dzon wrote:menubar ... displays the menu of the applications which you find in their windows

Sorry, I'm just too totally stupid to get it.
At what point / due to what action will a menubar display anything?
E.g., I put such a menubar on my desktop. Then I start some app which has a lot of menus, say Dolphin or Libreoffice. Now, trying to understand your explanation, I was expecting the menubar to "magically" start displaying the apps menus, i.e., those of Dolphin or Libreoffice ... which it does not. At least not for me. So, obviously I don't understand your statement.
Can you pls. give an example of what to do and then what to see.

dzon wrote:...same as global menu or system settings>startup>background services>daemon for menus (something).

Ok., so this daemon is running on my system. Correct. I was never aware of it nor of what it does? Could you please also explain the action of this daemon a little more.

Thx.

If you put some regular panel, right click it, add widget, search for global menu. Drag it there. Now, depending how you set it, it will either show the application's menu in a dropdown OR in a normal layout.https://imgur.com/a/V85lmNn

That daemon runs in the background to enable the global menu if you want it.

As a sidenote. Unless I'm missing something, the appmenu doesn't work for Firefox. Or all Fox'es for that matter ( Librewolf etc..). It does work in Chromium ones though, albeit sometimes still with a gtk glitch. Sometimes you need to open something else and go back to the chromium browser in order for it to appear. Same for some other gtk apps.https://imgur.com/a/ikvIhP7

Edit: Just saw you're on Suse. I believe they already patched it for Firefox. You'd need to look that up.

dzon wrote:https://imgur.com/a/V85lmNn

That made it snap! Thx.
Admittedly, I didn't even know that one can gather/organize menus of apps like that. Cool.
(Actually, now that I've seen them they kind-of reminds me of menus on macs. )

So I immediately tried a couple of my standard apps but had to realize that almost none of them actually did 'transfer' their menus into these panels.
So there seems to be no guarantee that Menu Bars / Panels will actually work as expected?

Well, it depends which apps that would be. Most of the qt or kde apps will probably work. Gtk ones is a bit of a hit or miss. Of the gtk ones it also depends what the developers have actually included as to show a global menu altogether ( firefox for example). On top of that, like I said, some gtk apps require a quick open-a-kde-app first-and-go-back kinda thing. It's a bug that's been around for quite some time. Mind you, it's vice versa. I mean, say you're on, I dunno, xfce. Same thing happens with the xfce4-panel global menu plugin...for qt apps. Here's an example(s). Gimp. No global. So if you're using a whole lot of gtk apps, there's a chance some will not work, or not at first.https://imgur.com/a/wlL8Bt9

Here's another example, Fsearch (gtk app). No menu at first. Till I open dolphin. https://imgur.com/a/mq6sCT0
But, I'm fairly sure that any kde app will show the menu.

Probably I just need to play around a little more. I'm not complaining. I keep finding apps that do work.
Some of those, which don't, include, Inkscape, Mathematica, Emacs, Blender (certainly an unfair example), TB and FF (not using Suse's, it's too old.), Geany, Master PDF Editor, Zotero, Gimp (as you also pointed out). There are certainly more.
But as I said, I think it's a cool concept.

Inkscape should work. It's just one of those click-something-else-first ones. While I used geany for a long time and I think it's a great tool, Kate is..um..mjam. And it does the menu.
https://imgur.com/a/frkm8cV