Drag files directly into any app's file selection dialog
02. Nov, 2009 
4 Comments
When you are in the file selection dialog box of any application (open, upload, etc), and you already have the file you want in a Finder window, you don’t have to manually navigate again to the file’s location. Simply drag the file from the Finder into the file selection dialog. This doesn’t move or copy the file, it navigates the dialog to the file’s folder location and preselects it.
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If you drag a file into a Save dialog, it will navigate to the parent folder and your file-to-be-saved will assume the name (and extension) of the dragged file. If you drag a folder into a Save dialog, it will navigate to that folder. If you click a grayed-out file in a Save dialog, your file-to-be-saved will again assume its name and extension.
I believe this has been around since Tiger or before.
I think I remember this being the case going back to OS 8 or 9. It is great though–I use it all the time, and FWIW, it works with Path Finder as well.