The current filtering in AGOL works well when working with small datasets and simple querys, but when you need to filter by a lot of parameteres, for the same field or different fields, it becomes cumbersome! Simple aditions would be:
Add "IN" and "NOT IN" operator for fields;
Permit user to intreduce it's own query (free SQL);
Permit fitlter based on selection from the table/map;
The best solution would be a search by attributes similar to what we have in ArcMAP.