Hello there.
Thanks for your answer.
I am not sure exactly what solved it, but I did change theme folder name, did deactive theme. It didnt help.
I then manually deactivated some plugins by renaming the folder. It didnt help.
Then I deactivated all plugins by renaming all plugin folders. Now the plugins were visible again in the plugins list. I did delete som plugins I dont need and started to activate the plugins again one by one.
Now all plugins I need is activated and It still works, I can see them in the list.
So probably something went wrong with a/some plugin(s) that created this.
I am now more careful doing backups before installing new plugins so I can more easily go back in case something similiar happens.
Thanks a lot for great support!