You don't. IMHO you shouldn't.If you have blah.html generated from this.tpl and blah.xml, if you regenerate it, TS should use the exact same set of files during the regen. It would not make sense to not use that.If you really want to choose, you would need to remove the PrimaryPT EA that TST places on the output.
That make no sense, I just tried it (6.7.1 SP1) click generate on blah.xml, asked which TPL to use and generated. Clicked generate again on blah.xml, it asked which TPL and worked again. What OS & TS level ?
Yea the GUI remembers the last TPL you generated with...
You can reset/modify last generation memory from "Form Settings" (Control next to Save, Save As...)