function onInstall(e) {
   onOpen(e)
}

<!-- language: lang-js -->
    function onInstall() {
       SpreadsheetApp.getUi().createAddonMenu()
          .addItem('Browse My Add-on', 'browseMyAddOn')
          .addToUi();
    }

    function onOpen() {
        SpreadsheetApp.getUi().createAddonMenu()
          .addItem('Browse My Add-on', 'browseMyAddOn')
          .addToUi();
    }