Magecraft from the Mark of Making Eberron subclasses

You can create a temporary magic item out of common materials. Choose a cantrip from the wizard spell list. Describe the item connected to it. As long as you possess the item, you know that cantrip. At the end of a long rest, you can replace it with a new item and select a new cantrip from the wizard spell list. Intelligence is your spellcasting ability for these cantrips.

 It should be able to be changed like spells are, but currently it can only be chosen when editing the character.

This is not a bug. There isnt a way to change race or class feature selections without going into the builder. They already plan to remove the builder in the future (and make just the character sheet be where you make amd edit the character).