Hello there, @RKazort.

Yes, we can set up a combined tax rate at the bottom of invoices. We'll only need to add a combined tax rate on the Taxes page. To guide you further, please follow the steps below:
 

1. From the left menu, select Taxes.
2. Under the Related Tasks list on the right, select Add/edit tax rates and agencies.
3. Select New, then choose Combined tax rate.
4. Enter a name for the combined rate and the different sales tax requirements.
5. (Optional) Choose additional components.
6. Select Save.

The new rate appears in the Sales Tax Rate and Agencies list. See the sample screenshot below:

Once done, you can now select the new combined rate in the invoice. Go to the +New button and select Invoices.

Also, labeling the first line as a convivence fee and another line as a state tax with the appropriate percent would be fine. However, I'd still recommend reaching out to your accountant for additional options on how to handle this matter. They can give you more advise for sales transactions and taxes.
 

If you not seeing the same options I've shared above, probably, you're using the Automated Sales Tax.  I'd recommend checking this resource to learn more: Set up and use automated sales tax in QuickBooks Online.

If you need more help with this, just comment below. Take care and stay safe always.