I found a curious thing in Windows 11. If you want to edit Normal dotm you can't simply right-click it and click Open in the menu. This does not open it

. Instead, it creates a new document!
You can however use this procedure: Right-click Normal dotm, choose Show more options (F2) and then click Open. It opens, ready for editing.
This probably applies to other templates as well, but I haven't tried it yet.