drop down menus in the invoice section "ADD FROM INVENTORY" (NOT the add manual item)
On the invoices in the ADD FROM INVENTORY section you can type the item your looking for which is fine for general purpose, but if you have a common named item with 100 or so variations of that item, you have to scroll forever to find the one you want. So why not enter the item name, then have a drop down menu(s) to select a variation, and it have the ability to add additional drop menus if further variation selection is needed.
search bar --- main Jet
drop menu 1 --- mikuni or drop menu 2 --- keihin
menu 1--- round menu 2 --- hex
menu 1--- short menu 2 --- long
menu 1--- # size
I have a similar problem - The solution I have come up with is adding the variation I need - by the name I call it - under the notes. But in your case, it looks like that wouldn't help much.