'Manufacturer' field is sort of supported now as well. It was it's own column originally but is currently parsed and added in front of the part number. This was done to allow multiple manufacturers and manufacturer part numbers per line like in this Arduino Uno BOM. Recently I have been considering the convention to separate the manufacturer and manufacturer part with a : like so:
References
Qty
Description
Part Number
Part Number
C9, C11
2
22pF capacitor ceramic
Johanson: 500R14N220JV4T
Multicomp: MC0603N220J500CT
The alternative I am currently considering is putting the manufacturer field back:
Split out from #2
The alternative I am currently considering is putting the manufacturer field back: