If I understand the goal correctly, you can create stacked box plots by adding the level of detail dimensions to the Rows shelf before Metric1, and then manually create box plots. I've attached an example I creating using data similar to your provided sample data.
I hope this answers your question!
stacked box plots.twbx 27.0 KB
This is very intuitive and exactly what I was looking for, worth the wait for reply.
Thanks for going the extra mile and putting together the workbook.
Closing the thread.