How to add link in File Open/Save Dialog?

I often attach files to outlook which are hosted on network drives. I typically like to add a UNC instead of the old-fashioned drive letter.

When I go to the attach or insert file dialog, I want to quickly navigate to one of several preferred server directories.

Is there any way I can add one of these directories to the left side of the dialog so that I can click on it directly? (I tried dragging the folder icon but that doesn't work.)

I've googled and not found any solution so far. (This is somewhat trivial in both Dolphin and Nautilus.)