Compact 1x1 loaders that use electricity. They are able to use separate filters on each belt lane, and can stack items on belts if stack inserters are available.
Mods introducing new content into the game.
Augmented or new ways of transporting materials - belts, inserters, pipes!
Entities which interact with the circuit network.
Support for "Spoiled Priority" just like inserters.
This is a limitation of the Factorio game engine. You'll need to make a request via the forums.
See: https://forums.factorio.com/viewtopic.php?f=6&t=123463
