editable box/drop down menu for t-shirt size

the shirt options don't have what we need, so I have to use the "shoe" column for our shirts which means I can't easily add this to an order but have to retype and remake the list every time.

the other option would be if we could edit the drop down list to include the sizes we need.

I think a blank editable box would be much easier to program and use.

Thank you for your time.

Donna Henry