I’m sure your LPD8 will send different MIDI messages than your APC MINI MKII. I don’t know if Rekordbox allows for simultaneous use of multiple controllers, but if they do, they would need to be mapped to different MIDI ports. If they don’t, then you could use Bome MIDI Translator Pro to merge data 2 and from both of your controllers but you would probably need to translate messages so that the messages match what RecordBox wants and that the appropriate LED Feedback goes back to each device on the MIDI port your are using to connect to RecordBox.
See below diagram.
There are also examples on this forum of connecting 2 APC MINI MK2’s to other applications. This one comes to mind but you can search and maybe find better examples.
Steve Caldwell
Bome Customer Care
Also available for paid consulting services: bome@sniz.biz