Setting up environment variables for GUI apps?
I don't believe variables set in the environment are going to work in the Open &amp; Save dialog box (OSDB). It's a nice idea, but you'd have to admit, kinda neckbeardy. 

The Macintosh way would be to use the Favorites list presented on the left of the OSDB. Drag your often used directories there and you have one-click access. 

A much more powerful alternative is Default Folder X. This gives you an incredible degree of short-cutting and changes of default behaviors in the OSDB.