This is a Plugin for the Glyphs font editor.
Download the Save & Export.py file and copy it to the Glyphs scripts folder (~/Library/Application Support/Glyphs/Scripts or Script > Open Scripts Folder from Glyphs)
Open the Keyboard Preference Pane in the System Preferences. Click the Shortcuts tab.
Click App Shortcuts in the left pane
Add a new shortcut by clicking the + button.
Select Glyphs
Menu Title is "Save & Export"
Choose a keyboard shortcut.
Finally, click "Add" to save the Shortcut.
You can now save and export with a single keystroke.
Uncomment Line 24 in Save & Export.py to switch to the last used application after exporting.