How to use entry data? My question:
How can I use entry data in the craft backend?
An example for the use-case:

Author creates an entry for the section &quot;Generate item&quot;. The entry has only a title/single word.
That created entry should be shown as a selectable item in a selection box.
Users can upload pictures and can select this newly created item in the upload form.
So pictures should get associated to the selected word.

I'm aware that I can use element queries in PHP or Twig.
My problem:
The use-case is simply that I need categories/entries should get created by authors (that have no access to real backend) and these should be relatable to another entry - but on the fly.
Thanks in advance for any kind of help!
You can't use entries from the control panel in other control panel fields without the use of a plugin. The only plugin I'm aware of that does this is https://plugins.craftcms.com/craft-dynamic-fields.
Depending on the use-case, which I don't totally understand, you might look at using an Entries or a Categories field too if you just want to relate an entry to another entry.