In google sheets from the table with items and its availability, I'd like to create a drop down list in a way to see only available items - so as in example on the drop down list i'd like to see Items A,B and E only, preferably with the corresponding quantity.
put this formula in Z column and create dropdown via data validation from there referencing Z column (then you can hide whole Z column > right click on column > hide)
=FILTER(A2:A; B2:B>0)