After you have mounted it via terminal command:
just navigate in Dolphin to
“Devices” … root … and then to the directory called /mnt
There it will be …
dir just lists the contents of the current directory - which will be /home/username by default if you did not explicitly changed it
In Linux I’d use pwd - it prints the directory you are currently in.
(pwd: print working directory)
cd /
brings you to / (which means: the root of the file system)
cd /mnt
brings you to the /mnt directory …
That probably sounds stupid but I have no idea howto navigate to Devices in Dolphin. Devices is a menu on the left side.
There are - in the left pane - a few categories:
light shaded font
Places
Remote
Recent
Devices
under Devices you find … your disk device, your device which contains your / (root) file system
That is what I see - I even started Dolphin in english to be able to accurately report what you’d see on an english language system … 
Very kind of you! I am using english so that I do not have to switch languages when encountering problems 
Sorry I thought you meant I was supposed to see sdb4 under devices already or I could manually add it to devices. Is that not possible?
I don’t know - nor do I care … 
I don’t know Plasma very well and only currently use it to be able to describe to you what you would need to do, where you would need to “click”.
What I said is:
you’d see a little tool tip when you hovered the mouse cursor over the respective entry - and that would (probably) show you the device name.
It did so for me …
Ofc it does for every drive that is there, but sdb4 isnt there and I dont know howto get it to there. But if the one in the mnt-folder is sdb4 then I can try copying settings. The drive itself is not in mnt but since the home folder is from 2022 it seems to be sdb4.
but again I come back to what you said:
You said you can mount it via the command line.
You said you could, you said you did.
And if and when you did - it will be under /mnt
So maybe you overlooked some (error) messages and only believe you did mount it.
It’s why I suggested to fsck the partition.
I did the check already.
Like I said, when I go into the mnt folder I see folders, not the drive itself. All I was saying is that it would be nice to just see sdb4 under devices, but the folders in the mnt-folder will do just fine.
Of course you see folders - it’s the contents of that drive that you see.
I don’t know what to make of your fixation of seeing something like sdb4 somewhere.
Navigate to
/home/username
or to
/etc
within that directory structure you see there
To be honest:
I’m about to loose patience and leave for good.
This is not a chat room.
Ask SPECIFIC questions that you might have.
It has the advantage that I know I am actually on the right drive!
I was wondering that this didnt come earlier.
Well you helped me very much so thank you!
But you already know - you (by what you said) just mounted that very drive and partition via command line - to the directory /mnt
What else would be there if not the contents of the partition that you just mounted?
(it’s actually a rhetorical question …)
You are welcome - the perceived learning curve just doesn’t seem too steep
Good luck!
See my earlier post where I describe how to reveal any hidden devices.
It seems I have over read this one. It has a name but no label. To me that was the same, I thought because I see it as “Manjaro” it already had a label.
Maybe it will now show up under devices. Thanks. edt.: it still does not.
I cannot find a post like that on this thread.
Look again. You even acknowledged it with a 
Show All Entries is the option label.
That just shows all the folders I have been hiding, but no more drives under devices.
I did that with almost all of them 
Oh well, it was at least a possibility.
This thread can be closed since I couldnt find the culprit and reinstalled.