Is there a list somewhere of any additional variables we can put in either the record of the form submission to the admin or in the email for the user who submitted the form?
I see there's %IP%, wondering if there's any others I could use, specifically the date and the ID number of that submission. I'm using the form to send an event ticket and would like to have a unique number on each ticket. Thanks.

Greetings! Thank you for posting your request!

Unfortunately Contact Form Builder does not have the functionality to add submission ID and user details to the custom text in email.

Looks like what you need is our Form Maker plugin. Although it doesn't add submission date, but Submission ID, IP, Username and User Email can be added to the custom text. You can test it on our demo site, here's the link:

goo.gl/G1MaLa

Navigate to Email Options and you will find these settings.
Thanks! Have a great day!