git blame on the file in the repository should give you the details.
In order for this to work you have to specify the route of the selected doctype as will be replaced later on.
if you are creating a Layout for an address you should use /app/address/
This should work like a charm, let me know if this solves your issue
If customising on a production configured site, you also need to do a:
bench --site <site> clear-cache