Smart View 11.1.2.1.300: Performing a subset operation
There appears to be no good way to filter on a subset in Smart View member selection (like you have the ability to do in the Essbase Excel add-in). For example, to select all of the business units, enter ENT_BU* (using a wildcard) into the search box on the Member Selection dialog box, go to the button to the right, click the down arrow, and select 'Check All Found'. This returns alot of additional members from the alternate hierarchies that are not needed.
After searching through knowledge base and documentation, I can see the way to filtering by subsets is for dimensions that contain attribute members, you can select attributes and set conditions for them to display only those members that meet these conditions.