Export Scene: the .tscn now shows the meshes. Before, each mesh was written as an empty MeshInstance3D node that did not use its .glb, so the scene opened in Godot with nothing in it. Each node is now an instance of its .glb (checked by loading the scene in Godot 4.7.2).

Fold Linked Duplicates -> MultiMesh now works in Godot. The MultiMesh has its mesh, written as <mesh>.obj (+ .mtl) next to the scene, and the instance transforms are written in Godot's format; the MultiMesh scene is also placed in the main scene. Before, the MultiMesh had no mesh and Godot rejected its transform buffer. Checked in Godot 4.7.2: four linked duplicates, turned and scaled differently, each within 1 cm of its place in Blender.

Objects folded into a MultiMesh are no longer repeated in the main scene as separate nodes, and the group's .glb is no longer written (the MultiMesh uses the .obj).

A linked duplicate folds into the MultiMesh only if the shared mesh is exactly what it shows and it stands still: one with modifiers, animation, drivers or children is exported as its own node, since a MultiMesh draws one mesh at a frozen transform. Texture paths in the .mtl are written relative to the export folder, not as absolute paths from your disk; options such as -s 2 2 1, which Godot does not read, are left out, and a texture from outside the Godot project is copied into <export>/textures/. A still object under an animated parent is exported as its own node, and so is a mirrored duplicate (negative scale: Godot would draw it inside out, invisible from the front), one whose shape keys are animated, and one that anything can move: its own or a parent's keys, drivers or constraints, an Armature constraint, a target moved by its own constraints, a path with animated evaluation time. A file in the export folder that this add-on did not write (your own bolt.obj) is not replaced: ours takes the next free name.