I'm not sure what you're referring to when you talk of tableau server and a datasource like tableau desktop. I think this might be a bit of confusion or an unrelated addition. However to not merge rows go to the analysis menu on the ribbon at the very top. Go to table layout - advanced. Then you should see several options concerning the maximum amount of rows or column levels.
I understand why tableau has provided this limit as too many items means heck you're just making a crosstab and most the time not the best use scenario. However I wished a window popped up as a warning when you put that 7th one on there and suggested what to do to fix it, if it was your intention to have all the things. I believe the limit was set at 16 from within this wizard last I knew.
Thanks for the reply.
This gets me most of the way to what I want, but the data source we're working with working with has about 30 columns and we'd just like be able to view it all.
Is there some way around the 16 columns limit?