I have noticed that, in the web maps, that users can create custom fields based on arcade expressions which shows as temporary field(s). However, those fields are only shown in the web map and cannot be used for setting a filter on the layer. It would be very helpful if a temporary field can be added that updates attributes in real time and be able to filter based on that attribute value.
Another option would also be for hosted feature services to have the ability to have fields created, based on an arcade expression, and used in the web map with full functionality.
If this already exists and I simply overlooked it, please let me know. Otherwise, I hope that this is something that can be implemented because it can be used for a multitude of the projects that I work on.