It would be really nice to be able to modify roads by adding and removing lanes to and from existing roads without having to replace them with another preset. Sometimes you just want two lanes, a bus lane, a bike lane (I know we don't have bikes yet, but we surely will soon, right?), and a right turn lane or some other specific configuration, for a specific stretch of road.
It would be nice to have a menu where we can pick what type of lane we want to add (or a button to remove lanes) and then be able to click on a road to add a lane where we click (such as between two existing lanes, or to the side of one) for that whole node.
Similarly, sometimes one might want a road to have a wide space on either side dedicated to street parking, with trees (they'll provide shade for the parked cars to stop them from turning into ovens, isn't that good?) and a wide sidewalk. It feels like it should be an option. Medians can also be added or removed using this same system.
I would certainly appreciate being able to just add a lane rather than have to try to find the right type of road preset that's the same but plus or minus one lane, if such a preset even exists.