Hi, sorry to bother you so soon again but I had this burning a hole in my head for a while. This is more me playing the ideas guy than a normal suggestion and is probably out of scope for the mod but I hope you'll indulge me for a second.
In factorio there's this unintuitive mechanic where miners dropping items on the middle of a tile, if there is a belt going directly to/away, will shift them to the right. This makes sense as there is no middle lane on belts, only right and left, but is a little confusing even for more veteran players. You can also abuse this mechanic to cheat a tiny bit with a mod like this by dropping items on the middle lane when you want them to be on the right and counting on the game to teleport them those couple extra pixels for a small throughput boost.
So why not (optionally) restrict drop positions to only the 4 corners of a tile? This is enough to make sure both sides of a belt are valid drops even on a curved belt, and would remove the invalid positions while slightly simplifying the interface to 4 drop slots instead of 9. It would however also necessitate altering default inserter behavior to drop either on the far-left or far-right position (and for consistency ideally also have miners/recyclers drop on the near-right or near-left position).
