When you specify material types in any of the construction dialogs it is a drop down box you pick the material from. However, go into the stretcher editor, and it is not only a drop down selection box, but you can also type in it. This is the only place I've seen you can type information into the material selection box versus just pick a material.
It wont narrow down the list, but you can type a letter/number and it will drop you down to the first item in the list with that letter/number. It will actually let you type more than one letter number. Ex. if you start typing 3/4 g, it will highlight 3/4 Generic in the dropdown list.