Same kind of question - if I want to upgrade a road from ground to elevated. I first need to change the road to something different, and then go back to the road I want with the attribute I need selected (ground, elevated, bridge) and upgrade back. With the older mods, we could just change the setting and use the upgrade road feature to change it

Upgrading the same road type to a different elevation level should work, and currently does for me, as long as "Anarchy" is active.