Select entities within a structure based on UDA (in a form like you can in smartview).

Summary:

For our customer I'm looking for an efficient way to slice and dice in forms. Currently I would like to see segmentation in a region (entity structure).

The region is reflected in my entity hierarchy (based on shared members). Segmentation is reflected as an Attribute of the primary entities.
Now, as a test I added the region as UDA, to see if I can use that as a way to create the required overview.

Question: how to use UDA on the entity dimension and be able to select all entities under a substructure that have a certain UDA on a FORM