First thing, cool mod.

Yet, I tried building a storage system and I cannot interact with the advanced item relays. No interface is showing up..

I just wanted to add. Shift+Right click, with an empty right hand does not interact with the advanced item relay, as long as you have a shield in your left hand.

Oh, yea, that's a vanilla thing though. Can't do anything about that :(

Sneak-right-click with an empty hand.