From @Pistro in the comment's section:

Two more feature ideas: 1. An option to retain modified segments and nodes upon road upgrade and upon connecting another road to a modified road; 2. Ability to edit lane positions in game, similar to the way it works in the editor. This would be useful when changing a road segment's width because lanes get stretched equally and things like props or parking lanes usually end up too far away from the curbs.

I second the "ability to edit lane positions" suggestion. it is a good idea.

Also, the ability to go underground, and to be able to edit train and MOM metro tracks.

It would be cool to be able to edit transitions (ground to elevated, ground to tunnel) of other networks (e.g. metro). In particular it would be cool to make the junction of that transition flat.

you can go underground in new version

> An option to retain modified segments and nodes upon road upgrade and upon connecting another road to a modified road

new version can do this (Elektrix mod not supported)

> Ability to edit lane positions in game, similar to the way it works in the editor

Sounds like another add-on to me. but modifying lane positions also changes the props' position.

> It would be cool to be able to edit transitions (ground to elevated, ground to tunnel) of other networks (e.g. metro). In particular it would be cool to make the junction of that transition flat.

new version can do this

I have been using the ALT select mode (for segments) far more than the default one for adding nodes, and it would be cool if I could set the segment selection mode as default.

"be able to edit train and MOM metro tracks."
This please.

@trumpet player

This mod can edit train and metro tracks since like a week ago, that came in the newest update.

Suggestions: Hover the node, then shift + scroll wheel to smooth corners, ctrl + scroll wheel to change the embankment.

Also, when you click on "make sloped" when selecting a node, it should make all connecting segments sloped, not just 2 at random.

I think what @trumpet player was suggesting and something I'd love to see too is flat or sloped intersections with rail and metro. One issue when trying to make smooth rail lines are road crossings, where they still have to be flat.

Suggestion would be a 'picker' function. In busy parts it's sometimes hard to select the right node.