Quick Advanced Editor Plus 2.1.4

Features:
Sceditor in quick reply
Sceditor in quick edit (setable in ACP, Default ON)
Smiley box in quick reply (setable in ACP, Default OFF)
Quick quote feature (setable in ACP, Default ON)
Auto Save Draft feature (setable in ACP, Default ON) (Only in quick reply, this plugin not made any modification in codebutton template)

Latest version: 2.1.4 (for 1.8.4 or above) (for Mybb 1.8.3 use 2.1.2) (for Mybb 1.8.0 use 1.8.1)

Auto Save Draft in New thread, New Reply etc:

This plugin not made any modification in codebuttons template. So you need made modification manually.
Check http://community.mybb.com/thread-156223.html

Link above is tutorial, so support of feature Auto Save Draft in New thread, New Reply etc only in tutorial thread.