I found the answer. There is an Advanced Configuration dialog within the Object Structure applicaiton where you can uncheck the "Exclude Parent Key Attributes" option for the INVENTORY object in my example structure (see screenshot below). What I find strange is that the BINNUM field on INVENTORY (default Bin) does not serve the same purpose as the BINNUM field on the INVBALANCES object (primary key value). So, in my opinion, this exclusion default behavior is erroneously excluding the BINNUM field in this structure - that they are both named BINNUM is just a coincidence.