You mean like the related tracks function?
Rekordbox - Transition tracks chain
Imagine that every track in a library has a custom list of tracks that perfect matches, basically transitions list.
You are playing Track A on Deck 1 and start to mix it with Track B on Deck 2, you like the result of mixing A to -> B, and you want to SAVE this result, you want to save this transition, for using in the future dj sets and mixes, so you add Track B -> to Transitions List of Track A.
When Track A is loaded in deck you can find in Transition List menu where you can find Track B.
You can switch view to Transitions Mind Map and see a Tree of Tracks that you added to custom Transitions Lists and build your mix with new level of prediction.
What you think about this new functionality?
Like related tracks but custom related tracks, that you can add manually by your self, when you load track A you can go to Custom Transitions list and see tracks that you added and for example you find there track B, you select track B and then you can see custom related track list (Transitions tracks list of track B) and you can build mix with more efficient prediction, you can see all possible trees all possible ways to build mix or dj set.