Perhaps in the case of a long stretch of belt. But as a new player every time it's caught me out it's been something like a little right angle before an underground or a few blocks before a balancer. Less immediately apparent.

Sort of, the issue I'm attempting to highlight is the player knowing they need to upgrade (that is having visibility that there's a single yellow belt somewhere in a sea of red or blue) rather than the process of upgrading itself.

Upgrade planner does address the latter, as does slapping down a new ...

Add a momentary input to hide items on belts.
While held (or toggled) this key would temporarily hide the display of all items on belts.

This would be a godsend when upgrading older belt systems before the blueprint slash and burn phase of the game. It's especially egregious with items like green ...