Thanks for reaching out to the Community space. Let me share a few things about the pre-made invoice template in QuickBooks Online.
QuickBooks has a standard template you can customize or use for all transaction types. Here's how you can find it in QBO: 1. Go to the Gear icon at the top right corner of the screen. 2. Select Custom Form Styles under Your Company. 3. Click on Standard.
You can also create and customize your own invoice template. Here's how: 1. Go to the Gear icon. 2. Select Custom Form Styles. 3. Click the drop-down next to New style and select Invoice.
In addition to using the built in editor to make your own forms for invoices, you can also go to QB Labs under the gear icon of your QuickBooks Online. from there, you can choose "Import Style"
What this does is allow you to import a template you've created with MS Word and map the fields to the fields that QBO uses. Basically whatever you design in MS Word should work once you import it into QBO. (see picture example of one I have done)
One major downside to doing this is that once you import your MS Word template, you cannot edit it using the tools in the template editor in QBO. If you want to change the template, you need to change the MS Word file and re-import it with your changes as a new template.
As @MarshallA mentioned, you can use templates you've created (or imported into) MS Word with the Import Styles feature. Click the Gear Icon and go to "QuickBooks Labs to enable the beta version. This gives you a ton of flexibility in the way you design and layout your sales forms.
From what I've read, what's important to keep in mind (in addition to what @MarshallA mentioned) is the data mapping component. If you ever run into problems using Import Styles, check how you coded the data!