Manual mode is designed for organizations that do not use standard G Suite and Office 365 messaging services.
This mode is therefore not synchronized with the service directory. This mode is specific to Signitic. You will be able to add and delete users manually only through the "My Users" menu.
This means that signatures and users do NOT update every night on your email services.
On the other hand, the Signitic desktop application allows you to retrieve these signatures and add them to your Outlook on Windows or MacOS.