How do you save Morphs as MAT files?

There's a tutorial at Poser Arcana on how to do this manually - www.poserarcana.com - tut by Chris Palomino. You can also find MAT Pose Edit in the free stuff section here by scourge. The latest version allows you to create MOR files though I haven't tried that out yet.

MAT stands for Material. A pose file that contains morph settings is a MOR pose. POS is position (rotations) - a pose Poser itself will save POS and MOR/POS poses. This is what the (+) in the pose library does.