How do I use a QuickBooks variable in a template for a recurring invoice - for example: a date of <duedate>+7 in CustomField1 so that it updates automatically?

Manual updating isn't feasible for 500+ invoices every month. Overall, the templates are very limited. With our former accounting package it was possible to include a product description that included the month & year in the form: "Service for %m %y" where %m %y would automatically convert to "June 2019" . This kind of macro substitution is so standard that I can't understand why the designers of QBO didn't include from the outset.

Thanks for joining in this conversation, @Billing Department. We're unable to provide a specific app for your business. Though, you can search for one in our Apps Center.

Simply click the Apps tab in the left panel, and enter a keyword in the search field to look for a specific invoice template that updates automatically. I'd also recommend reading the reviews first to give you more ideas about its features. 

You can also visit this link: https://apps.intuit.com/app/apps/home. 

Let me know if you have additional concerns. We're always delighted to help.