In firestorm there is a tool to export prim builds as collada files, I'm not sure if a similar tool is available in the official viewer at all. But this functionality is extremely useful for mesh creators to create scale mockups of their builds that can later be imported into 3D software like blender.

However, since blender is removing collada support as of Blender 5.0 a new tool such as this is needed. The GLTF uploader is great, but without a GLTF exporter it will complicate and hinder mesh creation in many ways.

I don't know exactly which viewers has had this features in the past or if it was only firestorm that had it, but it is something that would be useful and/or needed on all viewers, which is why I think it would be great if this was implemented in the SL viewer first since that will naturally spread the feature to third party viewers over time.

Personally I depend on exporting mesh in my workflow, so I will have to stay on Blender 4.5 until a new export tool is available that supports GLTF.