Turning items to subitems

How can I change an existing item to become a subitem?
How can I change an existing subitem to become an item?

Hi @AmirCodex - Welcome to the community! Currently you cannot swap item “types” between main Items and SubItems. However, this is eventually coming as SubItem functionality gets more built out. Technically SubItems are still in beta, so stay tuned for more functionality later this year and early 2021.