factorio
I remember seeing this in one of the tips you get when you start a game, but I can't find it again.
You're supposed to be able to "save" an item to a hotkey, so that no other items get placed there, and items of that type will get put there automatically. Anyone know how to do that?
While starting the game for the first time, I saw this option in the help.
If you have a requester chest you can set the type and quantity of the items that you want to be delivered there. I've never had robots put things in there that I don't want, however if it is a storage chest then the robots will dump anything that can't go anywhere else in there, this can clog things up if you have active provider chests as opposed to passive provider chests. I have never really needed to use active provider chests so I don't run into that issue.
Best Answer
You can set a filter to quickbar slot by middle-mouse button (clear by control middle mouse button). It can be changed in the options.
The same technique can be used to reserve some of the slots in cargo wagon for some specific items.