I'm looking for a way to use a workflow to send invitations to external users. Plumsail have a workflow action that enables this:
I've searched for this capability in Nintex but can't find anything. Does Nintex offer this feature?
As far as I know Office 365 Update Item Permission action does not allow you to grant permission to external user. This action does not work with custom permission level as well. You could use Send email action which includes HTTP POST link to update permission via REST.