You can pre-register the same visitor for multiple appointments. After you have created the first pre-registration in your visitor log, the second and subsequent pre-registrations will look just a bit different. When you paste in, or type, your visitor's email address, you'll see that we've remembered it for you with the little blue bar below the email entry:
You need to click on that blue, remembered email in order to add a new visit. If you skip that step, we'll give you an error message, which is just no fun.
When you type in that email, the recognition will take a moment or two to show up so give it a second to find the first registration and bring it up for you.