A new way to transport items and to build bases (now with filters).
Mods introducing new content into the game.
Augmented or new ways of transporting materials - belts, inserters, pipes!
Copying (right shift-click) the settings of a chest and pasting (left shift-click) to another chest will unlock the chest slot. This means that if you lock a chest slot to one slot, copying and pasting with shift-click will unlock the slot.