Overwrite vs. Append Output Mode
The API Connector add-on for Google Sheets provides two different output modes: overwrite and append. To access, click on the ‘Output options’ button.
Overwrite mode is selected by default. In this mode, the output of your request will appear in cell A1 of your destination tab, overwriting any data that is already there. This mode will also include the headers associated with your data set, in the first row.
Append mode will append results to the first empty row, and won’t print out any headers.
API Connector will pull in all data returned from the API, so when you use append mode, you generally need to set parameters to ensure you’re not pulling in duplicate data. Most APIs allow you to set a query string that filters by date or ID, which can be used to limit data refreshes to just new data. One useful technique is to reference a cell containing a date to automatically retrieve and append fresh data on a schedule.