Interdimensional Pipe

The Interdimensional Pipe is a craftable item that can be placed into Transition Portals. This turns it and it's corresponding Transition Portal in the adjacent dimension into Interdimensional Pipe blocks which will forward Forge Capability interactions between adjacent blocks on both sides of the portal.

They do that by mimicking the fluid storage, energy storage and item inventory of the block that is placed next to the Interdimensional Pipe on the other side. So hoppers, pipes and other machinery connected to the Interdimensional Pipe will actually see and interact with the resources inside that connected block.

Resource transfer will however only work if the chunk on the other side is loaded so it's recommended to place chunk loaders since Interdimensional Pipes won't force load chunks themselves. While the other chunk is not loaded, the Interdimensional Pipe will represent an empty fluid tank and Forge energy buffer with zero capacity as well as an inventory with no slots in it which makes it effectively a "brick wall" for any resource transfer.

When you don't need an Interdimensional Pipe connection anymore you can remove it by sneak-right-click with empty hand to get the item back.