With the 1.21 update on Bedrock, new Achievement rewards have been visible in the Character Creator. But sadly, even after being done with the new achievements, they can't be redeemed. This is because they have not been connected yet.

To find this, go to achievements. There you see the new ones, with no rewards. If you go down to the unowned items from Minecraft in Character Creator, you will see the new items that should be connected to the achievements.