There is a core magento page builder extension in magento 2.3.1 how to install this extension ? In my installation there is no such extension.I updated magento 2.2 to magento 2.3.1 maybe it is missing.
Pagebuilder is inbuilt in Magento Commerce 2.3.1. It is available for Magento Commerce only. To learn more about this please visit this link https://devdocs.magento.com/page-builder/docs/