It isn't uncommon for DJ's both structured and unstructured to realize that two songs sound good played into each other. These realizations can happen in practice or during performance, and as the music library continuously grows, it becomes increasingly difficult to remember these connections. As a solution to this problem, I propose track "linking", a method for creating many-to-many conceptual associations between tracks in the rekordbox library as a way of leaving a sort of breadcrumb between tracks.
The exact implementation would take some more thought, but using the feature would roughly consist of right clicking one track and selecting "add/edit linked tracks". This action would then provide some control for selecting any number of tracks to link back to the originally selected track. These links would exist bi-directionally and be shown in a "linked tracks" pane much like where songs can be viewed that are in a similar key, tempo, etc.
A feature like this would allow rekordbox to offer DJs a genuinely novel approach to mix in a semi-improvised format and navigate their library in a way unlike ever before.
More advanced implementations of this idea could include associating links with specific cue points in one or both tracks to make note of where transitions could take place.