Earlier, I was trying to create a "prioritizing smart inserter" -- that is, based on the order of the filters, the inserter would remove items from an inventory with a preference for items matching the first/left-most filter, and if none of those items were available, it would prefer items matching ...

Factorio 0.12.26

data\core\lualib\defines.lua


...
inventory =
{
...
furnace_source = 1,
furnace_result = 2,
...
}
...


Except, in a furnace, this is not how it behaves.

Put a {stone,steel} furnace down, add coal, smelt a few iron ore into iron plate, then without removing anything, add ...

Currently, it doesn't seem there is anyway to either:
a) Allow mods to register "slash" commands, e.g. /mymod dosomething 123
b) Allow mods to define global lua functions, so that something like /c myfunction("abc", 123) would work.

Of course, there are ugly workarounds, by requiring the user to ...