KOM, CR, Starred Map
When using the Segment Explore feature, it would be great to toggle on specific sets of routes that exist within the section of map you're looking at.
Three sets of routes that come to mind would be KOMs, CRs, and Starred segments.
It can be a lot of fun to target local KOMs and grow your "territory" if you live in a certain area, so it would be great to see how your KOM territory is growing and which segments you're missing.
The other similar feature suggestions that I could find date back to 2014 and 2015.