Tabletop Simulator script to import MTG decks
Mod available on steam workshop.
Load up the mod in tabletop simulator, and replace the existing script with your changes.
I recommend using this atom plugin that interfaces directly with the game - it makes script editing much more usable. Some shenanigans are required to get the #import statement to work properly - or, if you're lazy, simply inline json_parser.lua
manually when saving to TTS.