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 ("OpenWeatherMap" in this example), 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.