To set up custom search query parameters, follow the below steps Step-1: Navigate to Admin Settings of your GA4 property Step-2: Click on Data Stream and select the data stream for which you want to set up a custom search query parameter Step-3: An overlay will appear, like below, showing data stream details. It also shows details of enhanced measurement, which automatically tracks page views, scrolls, outbound clicks, file download, and site search. Click on the ‘Gear’ icon. Step-4: Click on ‘Show advanced settings’ under the ‘Site search’ option in ‘Enhanced Measurement’. Step-5: In the ‘Additional Query Parameters’ text box, type your custom query parameter that reflects in the URL when someone searches. Step-6: Click on ‘Save’.