Hi,
I have exactly the same question.
External User are described in the Licencing Guide for Saas.
And , we Don't know how to create them for Saas.
For On premise, we can change the Licence Type to External User, but when trying to login, an error occur.
with External Accountant Type, no problem when loging in.
So , For Saas, how to grant acces for External User ( like Customer , to let them access the Customer Card and some attached document ).