Acho que você deve conseguir remover o modelo não mais existente ao descarregá-lo. De < > Carregar ou descarregar um modelo global ou um programa suplementar no site de ajuda do Office:
Unload a global template or add-in
- On the Tools menu, click Templates and Add-Ins.
- Click the Templates tab.
- To unload a template or add-in but leave it in the Global templates and add-ins box, clear the check box next to the name of the item.
- To unload a template or add-in and remove it from the box under Global templates and add-ins, click the item in the box and then click Remove.
e de Sobre o carregamento e o descarregamento de modelos globais e programas suplementares :
To conserve memory and increase the speed of Word, it's a good idea to unload templates and add-in programs you don't often use. When you unload a template or add-in that's located in your Startup folder, Word unloads the template for the current Word session but automatically reloads it the next time you start Word. When you unload a template or add-in located in any other folder, it is unavailable until you reload it. To delete a template or add-in from Word, you must remove the template or add-in from the Templates and Add-ins dialog box.