Allow toolbar filter to be done with a key

[JayS]

I play factorio on a laptop and often don't have my mouse with me (mostly because I am so used to the track pad). I suggest that instead of needing to middle-mouse click in order to filter an item on to the toolbar, you can do a different process:
1. Put desired item in desired slot on toolbar.
2. Select item in hand
3. Press a key (instead of MMB, this would be changed in settings) to filter that item to that toolbar slot.
4. Be happy you didn't need to get out the mouse.

In order to remove the filter, you would still use the normal process (control + whatever key you binded)

[Phillip_Lynx]

You can change this already in the options.

Second page (Inventory), 5 field on the left (In german 'Filter festlegen').

See this picture.

[JayS]

You can change this already in the options.

Second page (Inventory), 5 field on the left (In german 'Filter festlegen').

See this picture.

Actually, you can't (change it to a key). I have tried and it says that this can only be mouse related. But once you said that I realized I could just set it to my right mouse button (which is mouse related so it is allowed) and still be able to filter things. Thanks!