I am trying to figure out how to add an inventory item(s) that has multiple attributes.   

For example, I am a florist and I want to track roses.  A rose is bought based upon color and stem length.  I added  custom fields (color and stem length).  I was able to add a rose with the attributes (Red, 70cm).  I tried to add another Rose with the attributes of Red, 60cm, but it says "Rose" has already been added