For working with the Reference Set members you need to open the Reference Set in an editor where the list of members can be viewed in a table. You can open a Reference Set similarly as a concept: by double-clicking on it in the Reference Sets View.
The Reference Set Editor displays members in a table with the exception of Simple type Reference Sets. Here, a
toggle button allows switching the view between hierarchical and flat list modes.
Reference Set Editor - view in hierarchical mode
Reference Set Editor – member table
Click on the clock button
to show or hide inactive members. This action is only available in flat list mode.
The Reference Set Editor allows filtering the members displayed in the Reference Set.