I have now figured out how to generate BOMs using my library field format. This was an unresolved issue in my previous installment Third Day with DesignSpark PCB. Older installments in this series are First Day with DesignSpark PCB and Second Day with DesignSpark PCB. Thanks to the DesignSpark team who encouraged me to retry some of my earlier attempts at generating a BOM in a different manner which eventually led me to a solution.