I know this was denied in #19 and #58 due to not wanting to add items to the mod to keep it simple. I respect the hell out of that philosophy, and I love this mod because it's simple and it just works.

My suggestion would be to upgrade chests by sneak + right clicking the chest with the items in hand. For example, upgrade a copper single chest to iron by sneak + right clicking with 8 iron ingots in hand, or 16 iron ingots to upgrade an iron double chest. Not sure how netherite would be handled, but this is my suggestion.