Unfortunately this didn't work for me.

I started a new game, was on the beach in Cyseal, saved the game. Extracted.

Extracted original save that I want to be able to play with the updated TreasureTable.txt.

Replaced original save meta.lsb with new save meta.lsb.

Game loaded to a blackscreen, then crashed back to Main Menu with an error 300 or some such.

I've tried thinking this through. WHAT tells the game that a save shouldn't use the files in Data\Public, and to instead use the files in the game's .pak files?

The time stamps?

I tried altering the time stamp on the original save's meta.lsb to no avail. It only made the save unavailable (red).

Admittedly I haven't exhausted all avenues of this theory by checking all the files in the save, and admittedly I'm not a little frustrated at this point. Heh. But like you said, welcome to the world of modding Divinity: OS.

Thanks for the help!