Adding line items to existing QBO invoice

We invoice clients monthly. We’d like to create a scenario that updates an invoice with each new order submission (using Fillout forms) as the month goes on. Currently using Zapier - doesn’t appear to be a way to add line items (it just replaces the currently line items). Has anyone been able to do something like this with a Make scenario?

Unfortunately this is how the API is designed. If previous data is not included it will not be included when updated. The App that is designed for quickbooks in Make and Zapier works off that API. Fortunately you can workaround this by recreating the previous entry and adding it back into the invoice. A few apis work this way.

Hope this helps!