Since your old External Bookings form is based on the projects you selected at that point, be aware that when you add a new Project, this one is not in your External Bookings form. It's very easy to add them.

Or maybe you want to delete one from the form?

Follow the next steps!

Go to Office > External bookings form.

Note: if your bookings forms don't show here, please refresh the page.

Click on the title to open your bookings form.

On the right you see: "Select projects".

From here you can select and deselect all the projects you want in your form.