🚀 go-pugleaf

Alex,

define in AI six swatches by spot inks (either
directly by Lab values or based on a swatch library,
numbers as well in Lab, not in CMYK).
Select all unused swatches and delete them.
Process K and registration black cannot be deleted.
These don't create separations (plates) if unused.
Save as PDF (all colors unchanged).
Test by Acrobat Pro: Tools > Print Production >
Output Preview.

If you want a separated PDF:
Print to Adobe PDF (not Export as PDF). Choose here
Separations (host based) instead of Composite.
This delivers six pages with separations, now in black
on white.

Best regards --Gernot Hoffmann