Using 1.15.2-6.1.0, I am unable to set defaultPayment to a tag, for example:

"defaultPayment": {
      "tag": "minecraft:planks"
    },

results in an invalid file and Parsing error loading Farming for Blockheads data file at .... in the log. It would be nice to be able to use tags here

That said, I'm not sure how it could show in the interface. Maybe "1x any minecraft:planks"?

I was actually just searching the same, though I want to use: tag:forge:ingots/copper

Thank you. I look forward to seeing this new feature!