https://mods.factorio.com/mod/belt-balancer-2?from=search

Belt Balancer is a pretty nice mod that lets you squeeze things closer together. I have no clue how much work it would be (as the belts connected decide the direction instead of the item itself, and it can be stacked to dynamically create larger splitters) but it would be phenomenal if Belt Visualizer could have support for them.

Copy pasting from the mod description:

2.0 added lane splitter capability to the engine, which means this mod will need a significant change to how splitter logic works. I have other mods I need to update/make before returning to this mod and adding full support, but for now they just render like regular belts so it won't break.