We are trying to copy the default Pages and Documents to another SharePoint subsite. In SharePoint online there is no option to make a template of these. In SharePoint Designer, we were able to make a template of the default Pages list, but it did not show up when creating a new App.
You can save the library/list as a template then create instances from sub-site:
Turn to classical UI then add an app, you will be able to find the corresponding templates.