FWIW, I haven't had to do this....
Anyways, Ignition's report generator is not dynamic. It isn't related to transaction groups, either. To get something like what you describe, you will have to create a report that uses a fixed set of column names for raw data, where that raw data is queried by script instead of binding, so you can post-process the column names into the names the report is stuck using. You'll have to use dynamic column widths so you can set unused columns to zero width (assuming a bit here...). You'll want to use dynamic column headings, too, to fake the displayed column names.
This discussion is relevant:
Maybe @justin.brzozoski will enlighten us further... (: