If you're editing NPCs inside their .MOD module files (provided by TSLRCM ideally), you'll need to use a save from before you enter the module you're editing. For example, if you're editing Luxa in 208TEL you'll want to use a save from before you entered that module. Even loading a Peragus save and warping to 208TEL will work.
If you do what I've just said and you can't see the changes, chances are what you've done hasn't been implemented properly.