This ArcGIS Online help page says that you can search for data by using the 'Location filter':
https://doc.arcgis.com/en/arcgis-online/reference/search.htm
And when you select 'Add', 'Search for layers' there is an option under Filter to 'Only show content within map area' but there is no filtering to that. I get way too many hits with the majority having no relation to the current zoom extents. This seems like it was working before.
