I think the StoredQueriesService in combination with expert search fits our requirement. Though it's not possible to store expert searches in the standard (default) yuuvis webclient, the API supports it well.
As said before our "Note" has a property 'keywords' of type Table:
1) get the correct field, simply get the correct index via '[IP]/_cat/indices'
2) get dmsObject [IP]/enaiored_1/dmsobject/[UUID]
3) the corresponding elastic field is 'str_note_keywords'
Now we are able to construct a StoredQuery:
let query = new StoredQuery();
query.expertMode = true;
query.term = "str_note_keywords:Bewerbung";
In this example it's the query for the keyword, aka Tag, "Bewerbung". In the UI we simply display all StoredQueries as Folders/Collections and implemented tagging functionality via Drag and Drop. In the implementation the terms are just concatenated (AND).
I'm just testing at which point I might hit some size restriction for the search term...