The experimental flag is only available for Shopify stores at this point in time.
How to enable drag, scale and rotate on your customiser
On the Shopify admin navigate to "Online Store" -> Themes -> Customize
In the Shopify theme editor navigate to the product/page/collection where you customiser is currently setup.
Click on "Sign Customiser" app block to bring up its settings.
Make sure "Use Experimental Features" is ticked.
Click on "Save" in the top right corner to apply your new theme settings.