Not a bad idea.
Personally though, I’d rather see a some type of automatic sorting function in the sample-list just like how the patterns are being numerically (all the samples connected to track 1 will be at the top etc). At least for me, it would made more sense upon browsing the tracks.
In the upcoming version, I read somewhere/if I’m not entirely incorrect, there will be a feature to group & color the samples. Additionally, I had the idea that these sample-colors could be automatically linked to the track-color (https://forum.renoise.com/t/multisample-handling-and-instrument-text-display/43791).
Moreover, it would made more sense (at least to me), upon browsing the tracks, the samples which are used there would be highlighted in the sample-list. But sure, it could be combined with your idea.
There could be even smarter solutions than this, but it would perhaps be better than the current system imo.