Basically selecting belt/pipe from UI allows you to change tier with Ctrl + Scroll Up/Down BUT when you do the same with belt/pipe selected from the building port arrows OR you place starting location then it doesn't work. Also "alternative route" gets stuck on active even when you release Ctrl key.
You could also indicate that it's possible to change belt/pipe tier with Ctrl+ScrollUp/Down when you select belt/pipe because it is not told anywhere except loading save tip.
You can check attached video. There is also audio when I click or hold Ctrl.