I have trail line data in a web map in map view in AGOL. I am symbolizing it by unique values to display different phases of the trail completion. After symbolizing in my legend I am able to see the trail phase. I would like to also add another field attribute to the legend which is owner. The problem I am having is that once I click add another attribute only certain fields show up and owner isn't one of them. Owner doesn't need to have it's own visualization in the map, I just want it to be view able in the legend. If I could figure out how to add visualization to both that would be helpful. Thank you.
I'm guessing that the OWNER_NAME field is also a text field? I don't think it's possible to have symbology based on two text fields in that way. See the "Change Style Quick Reference" table at Change style—ArcGIS Online Help | Documentation for more info.
One thing you should be able to do is use Arcade to combine the two fields into a new one on the fly or just calculate a new field that concatenates the two and symbolize based on that field.
Would that work for you?