Whenever a computer has "Require Windows/Mac login" enabled on the computer, the user will be prompted to enter their Windows or Mac login before they are able to connect.
How to Enable "Require Windows/Mac Login"
From the Splashtop Streamer app, select "Security."
From Security, select "Require Windows/Mac Login."
Once selected, the user will need to type in their Windows/Mac login credentials the next time they connect.
Here is the prompt that will pop up when you try to connect to a remote computer with "Require Windows/Mac Login" enabled.
Logging into a Local Account with a Domain on the Computer
Splashtop now allows users to log in to a local account without having to change the domain field.
You can follow this article on Logging in to a Local User Account on a Domain Computer
Logging into a Computer with Azure AD
This article will show you how to connect to a computer with Azure AD and if there is or isn't a Domain Controller How do I log in when the remote computer uses AzureAD?
Enabling Users to Save their Windows/Mac Credentials
The owner of the Splashtop team can allow users to save the Windows and Mac credentials whenever they attempt to connect to their computers. To do this, please log in to https://my.splashtop.com > Management > Settings. From there, you should see a setting that says, "Save Windows/Mac credentials (entered when starting a session)"
After entering and saving their Windows/Mac credentials, every subsequent time the user connects to their computer, they will not need to enter their credentials.
If the user does connect to their computer and lands on their lock-screen, they will get a prompt to automatically log them in.
How to Clear Credentials
If you no longer want to have the credentials saved, you can clear it by going to the Business application, clicking on the gear icon next to the computer, and selecting "Clear Credentials."