Hi,
When you set some specific macro into the settings, this one is resolved - so, you should use a macro which will resolve the Page title field. For example: {%pagetitle_orelse_name%}
.
This means that the value of the Page title field of the page is being looked up. Then, if you want to have some default value, set the {% CurrentDocument.DocumentName |(identity)GlobalAdministrator%}
macro to the root page's Metadata section.