Not clear. You've 4 rows in sample dataset. You want to join all rows into single row with comma as delimiter. Correct ?
What are the other dimension in your dataset. May be you need to stop at particular point and then start join operation again for every change in dimension value
For my solution you need to create 3 calculated fields. Maybe others have easier way to do this.
Please find the attached packaged workbook for your reference.
Sample (Solved).twbx 11.0 KB