Yes it's possible, but once you've switched from a local to an AD directory, then the create account button will only create AD users.
It's still possible to create new local accounts though, but you will have to use an Automation to do this.
Create a new automation and set the Task to Create Local User, set the Principal Name to your username and set all the other fields as appropriate.
Create the automation, then run it using the green options button then Run Now.
To create another user, edit this automation, change the details, save and run again.