You can enable experimental features from the top navigation bar if you want to beta test some new editor features.
To enable experimental features:
In the top navigation bar, click the Info & Tools () icon.
Click the Experimental Features tab.
Select or deselect features.
Click Apply to save your changes.
All experimental features are in beta, and users may experience bugs and or data loss. Please be sure to create a site backup before turning on any experimental features, and please report any bugs you experience.