How to add export formats to Preview.app? Is there any way to teach Preview how to export/save (and not just import/open) additional formats? If so, how?



As you may know, Apple has removed several export formats from the default dialog in recent OS X versions. They are still available if holding down Opt/Alt, though. Yay for “expert features”!



Default formats


JPEG
JPEG-2000
OpenEXR
PNG
TIFF


Additional advanced formats


ASTC
GIF
ICNS
KTX
Microsoft BMP
Microsoft icon
PBM/PGM/PPM
PVRTC
Photoshop
PostScript
QuickTime movie
SGI
TGA
The simple answer here is No. 

You cannot add formats because the libraries and support for those libraries must be compiled into the Preview application.  Since Preview is not an Open Source project, there is no access to the source code to add this support and subsequently compile it.

I investigated creating a plugin, however that also hit a dead end as there is no way to access the Plugin API (if it exists)  

https://discussions.apple.com/message/16054059#16054059

The best way to address this is to let Apple know about it by submitting feedback:  http://www.apple.com/feedback/macosx.html