You’d have to export back into Rekordbox. Engine doesn’t support that. 3rd party software does (some better than others), but its a big management task to sync both ways.
The problem with syncing back to Rekordbox is that Pioneer has a rather closed database (encrypted, password protected), so you would have to use XML export/import features in Rekordbox if you obey Pioneers rules. By my knoweledge, Lexicon is the only 3rd party software that really hacked into Rekordbox. I believe ATGR software relies on XML import/export.
Personally, I’ve come to a point where 90% of my gigs are at a residency or private parties, both where I bring my own gear, so I plan to swap CDJ3000s for Denon SC6000s if I should encounter gigs with Pioneer players in the fixed rig (connections are the same anyway, so…). But if that would still be 90% of my gigs (like 10 years ago, when I was young and athletic), this would be a big problem.