In AGOL Mapviewer we generally have filtering options like search by value, field or unique but the new mapviewer beta does not have that. Here is a quick comparison of both.
It is just a blank text input box irrespective of data types of the fields. It would be great if we have the categorization as we had in the past. I also couldnt find that in the road map for the new map viewer beta here Map Viewer Beta Roadmap
(or) If the option is already available in the new map viewer beta, please let me know how to find it.