"jquery-ui/ui/sortable" is a reference to jquery-ui version 11 only

[jaradc]

Just FYI:

                // AMD. Register as an anonymous module.
                define([
                        "jquery",
                        "jquery-ui/ui/sortable" // <-------------- this line
                ], factory );

nestedSortable/jquery.mjs.nestedSortable.js

Lines 18 to 22 in 1bbc818

	// AMD. Register as an anonymous module.
	define([
	"jquery",
	"jquery-ui/ui/sortable"
	], factory );

Sortable is in jquery-ui/ui/widgets/sortable in jquery-ui version 1.12 and 1.13.