If you need a custom login page created in mendix studio pro, you have to allow anonymous user. and give him the right to access that login page only (and set it as his default home page in the navigation)

Create a Custom Login Page: First, create a custom login page in your Mendix application. Design and configure this page according to your requirements. Ensure it has the necessary input fields for username and password entry.

Create a Microflow for Login Logic: Create a microflow that will handle the login logic. This microflow will validate the user's credentials and perform the login action. Inside this microflow, you can use the Login action to authenticate the user. You can add your custom logic for handling authentication and authorization before using the Login action.

Disable Anonymous User Role: In the Mendix Security settings, disable the "Allow anonymous users" option. This ensures that users must log in before accessing any part of the application.

Set Up Navigation: Configure your navigation to start with the custom login page. In the Navigation settings, set the "Home" page to be your custom login page.