There is no direct export option, however when saving in the .tif format, you can easily convert to separate .png files using Imagemagick's convert
.
If you save the following image:
in the .tif format without flattening:
and then convert to single images using:
convert layered.tif layers.png
you will then have the separate images:
Hopefully, installing Imagemagick won't be a challenge or two.
There also seems to be a script to convert from .ora, however saving as .org is very slow and a quick test of the script created results of much smaller resolution.