I was testing data pack features, and I discover a bug with custom advancements.
When we create an advancement, we can put a name and a description, but when we are in the game, the advancement name, description and new advancement tab haven't the name. They have advancement.advancementidname.title.
P-S: Is it normal we can't test data packs direclty into MCreator?
P-S 2:The new advancement system is really cool, but I suggest you to add to have the "AND" and "OR" procedure block. With this, we will be able to make an advancement when the player will have entered into each biome (or a selection of biome).