You can turn on the test mode to check inactive recommendation boxes on your site safely. Take a look at the top right corner on any subpage and click on that little setting cog. Here you can turn on/off the test mode. Turn the 'Test Mode' switch on.
The test mode is turned on/off only for your current browser in which you are using the Dash. If the test mode is turned on successfully you will see a small notification in the upper left corner of your site.