Entra ID and Microsoft Graph Extensions and Attributes
This table is a comparison of the five different types of Microsoft Entra ID + Graph extensions and attributes.
I created this view since the Microsoft docs don’t include all this information in a single view (especially the Custom Security Attributes).
Source: Comparison of extension types - Microsoft Learn
1 Multi-value support in directory extensions is limited to attributes synchronized from on-prem. It is not possible to create new multi-valued directory extensions in Azure AD.