showSidebar(userInterface)
Opens a sidebar in the user's editor with custom client-side content. This method does not suspend the server-side script while the sidebar is open. To communicate with the server-side script, the client-side component must make asynchronous callbacks using either the google.script API for HtmlService or server handlers for UiApp. To close the sidebar programmatically, call google.script.host.close() on the client side of an HtmlService web app or UiInstance.close() from a UiApp web app. For more information, see the guide to dialogs and sidebars.
The sidebar will display on the right side of the editor for users whose environments use a left-to-right language and on the left side of the editor for right-to-left languages. All sidebars shown by scripts are 300 pixels wide.