I think it's supposed to be used to do something like split a network double solid line into two singular lines.

Once you designate a point as 'split', attach a line to the point. Then when you look at the line details, above it it should say 'right/center/left'.

I don't know if I am using it wrong, but this feature never seems to work for me. I get the point to split and I can set offset etc, but how to actually have the lines connect to the splited points?