Complex Model Workflow Using Mixamo

Mesh Preparation: Combine all individual meshes (hair, shirt, trousers, etc.) into a single mesh.

Export Options:

• Export as .obj if you don't want materials. This is proper because reducing it causes AI assistants to work less. 
• Export as .fbx if you want materials containing textures (when exporting, you must zip the .fbx file and texture.png/jpg together)

Upload to Mixamo: Upload your model to Mixamo for rigging.

Download Options: Download the rigged file with mesh connected to bones:

• .fbx binary format (for large bones)
• .dae format (for small bones)

Import to Blender: Import the downloaded file into Blender.

Adjust and Arrange:

• Clear transformation scale(Alt s)
• Apply transform (shift a) only a rotation in an armature and mesh 

Export to Godot: My case selected .glb or .gltf