I don’t think that these 3D formats support groups. Hence they cannot be exported.

Hey @ws614274, as a slightly more helpful workaround than the previous answer, what you can do is use the hide icon (the small eye) for each group. Mecabricks only exports groups that are visible, so you can hide and unhide the groups that you want to export and group them in your chosen 3D application on import. A bit of work, I know, but it's the best solution that I know of at this moment in time (and probably for the foreseeable future).

^^ What Hiro20 said... in addition, if I have a complex model I will toggle off every other group so that nothing is touching. I export that and then go back through and reverse which groups are hidden and which are not. That way it only takes two import and export cycles between Mecabricks and Blender. When I get into Blender, the separation of the parts makes re-creating the groups much easier. I'll import the first half of my model and move the pieces into collections. The physical separation makes box selecting my intended groups much easier. As I move parts, I hide the collections. When I'm done with this, I'll import the other half and go again. Mecabricks exports remember where the parts belong in space, so when you do multiple imports, everything will land where it should. Here's a picture of how I broke up Wall-E as an example.

Thank you @B1Trash, that's a great solution! You're right, I actually forgot to mention the moving parts to collections in Blender, that's quite an important step for an organised blend file. What might also be a helpful tip is if I'm building a symmetrical model, such as your awesome Wall-E, and you're only going to export to Blender for rendering, I only create one half of the model in Mecabricks and use the mirror modifier in Blender for the symmetrical parts (in collections). This saves a huge amount of time and I think if the mirror modifier uses instances, a huge amount of memory.

Thanks for the helpful comments... I figured out a very similar solution along the lines of what you have been proposing... anyway, good to know that you guys obviously faced similar challanges 😃