I can sometimes get the scrap filter (black and whitelist) to work with an inserter onto a belt, but inserter into chest, recycler, or splitter does not seem to work.

Edit: NVM, was using the scrap result, not scrap

I should figure out if I can hide that from lists to prevent stuff like this. Sorry!

Possibly related, I've noticed that when sending recycler output to a chest, and having two inserters coming out of that chest, one whitelisting wanted items, and one blacklisting those same items to get everything else, well... the blacklist inserter grabs the "scrap-recycling" item, which then is instantly (within the same tick) converted into something else, possibly including something that was in the blacklist.

Because i'm curious, I'm going to poke at the code and see if I can find a suggested fix... and in the mean time, I might undo your hiding, so I can blacklist the scrap result -- pity that'll take one of the slots, but I guess it's worth it as a workaround, if I or you can't find a better fix. :)

Yeah, I don't think you're going to find a way around that.
The item spoils after one tick, any less and it either wouldn't spoil at all or using other shenanigans, or wouldn't produce an event in order to replace the item.
I can make hiding it a mod setting, but it would require a reload every time you wanted it to change.

Well, I found a solution that works for me. In data.lua, I changed "hidden = true" to "hidden_from_player_crafting = true", and while that doesn't "fix" it, it at least lets me select Scrap Result in the blacklist filters (from the "Unsorted" tab, with just that change; not sure if it'd be better to put it in with the intermediates). Maybe that's an acceptable change, I dunno... or maybe you could make that change depend on the mod setting. For me, I'll just play that way for now. :)

I've unhid the scrap result item again in 0.0.7, but it has a new icon and a dedicated place in the GUI.
Hopefully this will allow people to be able to filter for it and still tell the difference.