Rob Collie shows an easy method to concatenate selected values for display in Excel and Power BI:
Measure Step 2: Dealing with No (aka All) Selections on Slicer
The original measure above is really awkward when the user has made NO selection on a slicer – because it can then return a REALLY long list!
To deal with that case, we add an IF to the measure to detect precisely that case, and then return “All.”
Read on for the code, as well as some caveats and additional hints.