Hi GrantTheGoalie,

QuickBooks Online is the go-to program for business owners that are looking to manage their invoices with ease. It's important you're able to edit your invoice so you can continue to do the things you enjoy. Don't worry, I'll be happy to share more info and make sure you're on the right track with achieving your goals. 

When it comes to editing an invoice derived from an estimate, it's important to make sure both the estimate and the invoice are matching. This means you'd have to also edit the root of the invoice which is the estimate. You can edit an existing estimate/invoice by clicking on Sales > Estimates/Invoices > locate and open the form in question > from here you can edit your invoice accordingly. Once you're done, make sure to save your changes. 

Let me know if you have additional questions by leaving a comment below, I've got your back.