feature suggestion:load existing html into the menu

feature suggestion: just load existing menu into the menu
don’t copy menu , copy menu add the page size.

Please add option, so can just load the main men.
like the sidr sample code:
https://www.berriart.com/sidr/
$(document).ready(function() {
$(‘#existing-content-menu’).sidr({
name: ‘sidr-existing-content’,
source: ‘#demoheader, #demo-content’
});