On trying to learn new features in Rebrand-Ui , generated doc path through Document Custom Layout is still need to be changed. This issue at many other places has been resolved recently. Need attention to it too , I accessed the doc by revising path. thanks !
I got turnaround by changing in doctype_layout.js file.
from window.open(/app/list/${frappe.router.slug(frm.doc.name)}/list);
to window.open(/app/${frappe.router.slug(frm.doc.name)});