For some reason I can no longer search for keywords. Some keywords do not work at all. Others are only partially displayed (i.e. only a part of the documents that are tagged with the keyword will be displayed). It’s totally weird.
I’d first double-check the search settings (click on the blue magnifying glass icon to the left of the text), and make sure things are set up to exclude some documents. For example you can set search to only look in the Draft folder. There is a command at the bottom of the menu that will reset all options to default, which is often the best choice.
No, It’s definitely a bug. I’ve tried all of your suggestions. They did not work. Maybe the problem is that I created the file in Scrivener 1 and than gave the Beta a try. If I, however, create new keywords and attach them to documents, the search functions quite correctly.
When I add an old keyword to a document (like Exkursionen), that means a keyword I’ve allready created in Scrivener 1, it will not be displayd in the search section. If I, however, add a new keyword (like Exkursionen-1), everything seems to work quite well.
Update: Nope. I closed the file and restarted it. My new keywords (Exkursionen-1) don’t work anymore. 
I can search inside the documents, but not for keywords. That’s kind of ruined my work. 
Okay, in that case, the second thing I’d look into is resetting the search index. It could be something in the upgrade process caused that to happen incorrectly, and if that appears to fix it for you, we could take a closer look at that procedure and make sure it is bug-free.
The “search.indexes” file is located within the project’s Files folder. If you remove it before loading the project, it should force a rebuild.
Try File > Save and Rebuild Search indexes
Thank you so much! That did the trick!