We don't support adding new users directly to SignatureSatori because it would cause issues with G Suite synchronization.
The only way to add new users is to have them in G Suite and import them to the app.
- Go to the Users menu
- Click "Load new users from G Suite" below the list of users.
This option will load new users from G Suite and eventually delete the non-existing ones.
Please, don't click on the black arrow next to the button. This leads to an option for rewriting all users or groups in SignatureSatori. More information in What is the difference between refresh modes?