That’s where the 3rd party software like Lexicon, MIXO or DJCU comes in. Every DJ software uses a unique database. The softwares above convert the databases between different DJ softwares into a format that readable. These databases contain your saved hot cues, saved loops and playlists.
You can transfer this data between iOS and macOS devices using the djay Media Library database file. However, this data is only readable by djay. So, you can for example copy all of your My Collection playlists and saved Hot Cue from your iPhone to your iPad or from your iPad to your Mac and use it on another installation of djay.
There is no built-in tool within djay to export your playlists and saved Hot Cues to Rekordbox or any other DJ software.