How the Title already tells im thinking about an Trade-cheat. With this cheat you can see what the villager will trade even if its not unlocket yet. I dont know if this is possible, maybe with those "nbt" Data or Stuff like this (i have just a little experience at coding).
So you found a novice farmer whos buying wheat and carrots. Thats the normal thing you can see, if you enable the cheat you can already see what he will trade when he will be a Master-Farmer, selling golden carrots or melon or this stuff.
I hope it is possible bc i never saw this feature befor and it would be really nice to have it ^^
If its not possible please tell me why, thanks :3