Import FBX and convert to MMD model Open a new window, import the FBX (some say to select "force connect children" and "auto bone orientation", but in my test, enabling them caused issues), then ...

if the order of a model's materials can be sorted in the normal Blender way before exporting the model to pmx. Yes, Material Sorter is made for older Blender versions, and it lists MMD material's name ...