I am currently working with Experience Builder in AGOL. I have a roadway feature layer that has been published up to AGOL and is the data I am using in Experience Builder.
The issue I am having is with the edit widget within the Exp Builder. When I multi-select the roadway feature layer, the edit widget presents these records as a scrollable list within the edit widget.:
However, these records are not respecting the custom displayField expression that was set in the feature back in my pro document before publishing up to AGOL.
I have brought both my roadway feature and Exp Builder into ArcGIS Assistant to view the JSON code and see if there is a displayField I can edit; haven't found one.
I also opened up the REST services directory as Admin and tried updating the service definition:

My custom displayField string will consist of 4 string fields. Is this the problem? That the displayField can't handle more than one field? Anyone else been able to successfully update the displayField through the JSON, and change it to a multiple string expression?