Payment issue on registration form

I have a registration form that includes a section for Paypal payment for entry fees.

I would like to also have a section that allows users to use Paypal to pay for optional t shirts.

Jotform seems to want to place all payment items in one section, regardless of whether they are required or optional. The problem is, this allows users to register for an event by avoiding paying an entry fee, and just paying for a t shirt, for instance.

To have more customization over how your products are set up, you can set them up using regular fields like text boxes, check box fields etc.  You can then assign those options calculation values if needed:

https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

Perform calculations on those values/options:

https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form

Then pass that total to your payment field:

https://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field

This will give you much more control over the layout of your products.