According to this, it is "common in the Dashboard data profile" to "create a FeatureSet completely from scratch".
However, I have not found a way to add a FeatureSet with geometry properties to a dashboard map. From what I gather, this can only be done by adding a map that already exists (which has some layers in it).
Anyway to add a FeatureSet from an arcade expression that contains geometry information and can be mapped in a dashboard? That way I would join all the fields I want from different tables into 1 big table, map it, and have different elements react between them.
Thanks.