Can I add patterns from a Windows PC/Mac, etc?

es.
By using the dedicated software 'SQUID Manager', you can forward the standard MIDI files stored in the Windows PC/Mac to this unit and perform/edit them as patterns on this unit. Please use DAW software, etc. to create standard MIDI files.
You can also forward the patterns created on this unit to Windows PC/Mac as standard MIDI files.

You can download the latest SQUID Manager from here.

https://www.pioneerdj.com/en/support/software/production/toraiz-squid/

NOTE:
The specifications of the SQUID and MIDI files are not the same, so the SQUID patterns after the conversion may not be able to completely reproduce the original MIDI files.