Today’s update 5.4.3.6 adds a Send to Drafts service, and a share extension. Remember to activate the share extension and the service in System Preferences.
(macOS has a inscrutable method for deciding which share extensions appear in what contexts. The Drafts share extension will appear for selected text in Safari in the Share submenu of the contextual (right-click) menu, but not always in the Share menu from the Safari toolbar.)