I will take a look into it

Could not find any place to edit anything for warehouse, stations, buildings in general other than the actual factories themselves.
Only thing I could think of would be to create a custom factory that is hidden in the city that inputs all material types, but does not output them at all and has maybe 0-1 storage on it.
Would need it to not use any of the current slots though while still allow it to be "visible" on the backend

Thanks for looking into it and that sounds like a good idea but may be too deep down the rabbit hole for me!