First off, a caveat: I think the SQL Builder tool sucks and is totally unneeded, except on paper so you have it as part of your feature set. I wouldn't touch it with a ten foot pole. There, with that out of the way...
I don't believe you can parameterize the schema with the SQL Builder. I use the 'Generate SELECT from blah blah' option religiously and
always parameterize the schema. Trivial to do there. Perhaps you could consider a change in philosophy?
If you insist on using the SQL Builder tool to build the sql and insist on then being able to change the table's schema, you'll need to do it in steps. Generate the sql, copy it to the clipboard, paste into your editor of choice, make the schema change, switch the stage to Custom SQL and then paste your tweaked version into the stage.
ps. Been playing with this while posting. Looks like you have one other option and that would be to make the
entire "schema.tablename" a single job parameter. Then right-click on the table on the 'canvas' in the Builder and select Properties. Even though the tablename is Read Only, you can click on the ellipsis and then 'Insert Job Parameter'. At runtime, you could then change just the schema name in the parameter. Of course you could change the table name too but that would just make it blowed up real good.
