Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Cameras
GLTFIMPORTER_CAMERASParameter: Geometry
GLTFIMPORTER_GEOMETRYParameter: Normals
GLTFIMPORTER_NORMALSParameter: Phong Angle
GLTFIMPORTER_PHONGANGLEParameter: Vertex Colors
GLTFIMPORTER_VERTEXCOLORSParameter: UVs
GLTFIMPORTER_UVSParameter: Flip Z
GLTFIMPORTER_FLIPZParameter: Materials
GLTFIMPORTER_MATERIALS