How can I create an order form with multiple quantities with different sizes?

If you'd like users to select multiple sizes with the other product properties, you have to enable  Sub Products. Please refer to the following guide:

https://www.jotform.com/help/264-Create-Sub-Products-Based-on-a-Product-Option

Here's a cloned version of your form with this method: https://form.jotform.com/202667268379974. It's something like this:

Super helpful, thank you. I actually tried that but because I didn't see
that on the form design, I thought I used it incorrectly.
Stephanie Driskill
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