Hi @Hanny,
I couldn't find how to change the settings
The max number of indices that can be returned at Create Index Pattern
is currently hard-coded and cannot be configured.
how to delete old indices automatically (by date).
It sounds like Elasticsearch Curator is the thing you need. You can also check out this thread to get more info on that.
Let me know if I can help with anything else.
Best,
Oleg