Update extension in collection export filepath

addons/io_scene_gltf2/__init__.py

@@ -94,6 +94,14 @@ def ensure_filepath_matches_export_format(filepath, export_format):
 
 
 def on_export_format_changed(self, context):
+
+    # Update the filename in collection export settings when the format (.glb/.gltf) changes
+    if isinstance(self.id_data, bpy.types.Collection):
+        self.filepath = ensure_filepath_matches_export_format(
+            self.filepath,
+            self.export_format,
+        )
+
     # Update the filename in the file browser when the format (.glb/.gltf)
     # changes
     sfile = context.space_data