When you add Scripter to the Session plugins, instead of being saved in your scene, the scripts will be saved in your VaM folder: VaM\Saves\PluginData\Scripter\Session\.

If you switch to an external editor such as VS Code, you can edit the scripts and save them. When you switch back to the Session plugin, the scripts will be reloaded. Any scripts that were added will be added to the plugin automatically.

Note that there are no ways currently to remove a script. You can delete the file and reload.