This feature is available since OroPlatform v4.2.5. To check which application version you are running, see the system information.
If you have to support only the latest version of mainstream browsers, consider disabling Babel for the project by adding the below configuration to the config/config.yml file:
oro_asset: disable_babel: true
Enabled Layout Themes
To build only the themes that are in use and disable the rest, provide the list of enabled themes by adding the following configuration to the config/config.yml file:
oro_layout: enabled_themes: [acme_default_theme, custom_theme_for_german_website]