I'm here to straightened this out for you, @acmaj.
As mentioned by my peers, Colorado is one of the states that don't tax shipping costs, as long as the shipping cost is shown separately from the price of the item.
However, some states have special conditions and restrictions that can make the taxability of shipping costs more complex. If you'd like to record the sales tax as taxable, you have to enter them as an item.
Jen already provided these steps, but let me give some screenshots to help illustrate them:
For more insights, you can refer to this article: Create and use a products and services list.
If you're able to verify with your state that shipping costs should be taxed, please reach out with our phone team to investigate this further. Follow the steps on this link to get in touch with them: Contact the QuickBooks Online Customer Support team.
That should get you going today, acmaj. Let me know if there's anything else you need by adding a comment below. Have a wonderful day.