Create a custom extension attribute using the Microsoft Graph API and configure it to be synchronized with all applications and services.

Extend the Azure AD schema using the AzureAD module in PowerShell and configure the new attribute to be synchronized with all applications and services.

Create a custom attribute in Azure AD Connect and configure it to be synchronized with Azure AD and other applications and services.

Manually add the custom attribute to each user's profile through the Azure portal and ensure it is replicated in all applications and services.