You can add a new user directly from the Entry Editor. This user will be added to the user dashboard with an auto-generated email ID, which can be updated later.
Permissions to add Dummy users
By default, admins or editors do not have this permission. To grant this permission, go to the users_roles dashboard and add the "Create Dummy User" permission.
How to add user from Entry Editor
Next to the author field, you will see a blank dropdown. When you start typing, an "Add Author" option will appear. Clicking this option will add a user with the specified name.