I have deployed several versions of my web application in the Google App Engine. In the new Google App Engine toolbar, I could not find where to install the version as the standard version of the application. The old GAE console allows us to click the "Set as default" button, but it will disappear from the new dashboard.
In the developer console, select App Engine> Versions.
Select the version you want to use, then> Traffic Migration (at the top of the page).