Hi @bulli79,
Thank you for reaching out to us. I tested on my local setup and I also couldn’t select the tabs while editing post meta, it seems like a bug in the Essential Grid plugin, I’ve submitted this to our issue tracker so the developers will be made aware of it.
Alternatively you can access these settings (tabs) in post editor, simply edit your post in WordPress post editor, scroll down a bit to find Essential Grid Custom Settings and from there you can access all the tabs and change their settings:
You can also refer to following guide here https://www.themepunch.com/essgrid-doc/custom-meta-data/
Hope this helps!