This is a simplified workbook, but maybe it can work for your setup.
I think you were almost there.
It looked close to what I was following in:
I used this to concatenate:
IF ATTR([Lowest Value])="Lowest Value" THEN
IF FIRST()=0 THEN ATTR([Dimension])
ELSE PREVIOUS_VALUE("") + ", " + ATTR([Dimension])
Then this to get just the final tag:
IF ATTR([Lowest Value])<>"Lowest Value"
The table calculation settings are shown in the below screenshot.
Attached in the forum thread is the workbook v.10.3.
275433concat.twbx 27.6 KB