This video shows how to use "Part Number LCSC" additional field in BOM for assembly in JLCPCB.
The additional info is here:
https://support.jlcpcb.com/article/80-b ... t-assembly
https://support.jlcpcb.com/article/79-p ... t-assembly
https://support.jlcpcb.com/article/140- ... n-diptrace