@m2m - It's not possible to automatically in the current export mechanism. But I agree, that it would be a useful addition... especially for animations!

Did you know there is a workaround for this? Since the export only works for visible bricks, you can hide all of the bricks except your group and then export just that group. Then hide that group and un-hide another. It will take some time, but if you need groups in Blender, this will work. The good thing is that the geometry stays the same, so when you import your different models into Blender they'll line up back where you left off. It can be a long process to do if you have a lot of groups, but depending on what you're doing, it may be worth it.

@B1Trash - Thanks for the feedback and workaround. This is indeed a little tedious, but does the job for smaller projects.

@Scrubs - Maybe thats an enhancement you could consider. I think the easiest way to do would be to add a "groups" section to the json structure, where each 'group' has a name, id and list of parts within that group. This would be most likely least invasive to the current file format.

Many thanks.