Installation The Khronos glTF 2.0 importer and exporter is enabled by default in Blender 2.8 and higher. To reinstall it — for example, when testing recent or upcoming changes — copy the ...

The emission map is more straightforward, the exporter could look for the emission Blender node, which is separate from the Principled BSDF node, but presumably could still be located in the node ...