...
Filling the form as below:
Click "SAVE"
Add the attribute mapping for the "id_token_hint | iod" attribute
Click the context menu 
of the newly created Service Provider, e.g. "EntraID EAM", select "Edit" from the menu, then select the "Attributes" tab
Click the "CREATE" button to create a new attribute
Fill in the following properties
Click the "SAVE" button to save the new attribute
Click the "SAVE" button again to save the change in the attributes