Save file to hidden directory with standard OS X save dialog
The built in way to do this by using a key combination when in the save/open dialogs to toggle the hidden files to visible or hidden



Update: This shortcut works in all views, But in column view it does not update the view to show the change until you navigate to another directory.
Not sure why this is the behaviour.
But you can toggle it in column view click on another folder (in the parent column on the left) and back to see it has changed.



When you are in the Save or Open Dialogue of the app.  

Press and hold the CMD + shift  and then .  keys at the same time.

This will toggle hidden files/folders in the  Save or Open Dialogue.



[toggled to hide invisible files/folder]





[toggled to Show invisible files/folder]





Note: You do not need to have hidden files/folders set to visible in the finder
This toggle works independently.