If the user can select the parent, this is only possible for the creation of a site. The edit interface of an active site will only show the path of the parent.

At the project level we can use the following configuration:

ez_platform_site_factory: 
    templates: 
        ez_conference: 
            ...
            parent_location_id: 62
        ez_roadshow: 
            ...
            parent_location_remote_id: 1548b8cd8dd4c6b5082e566615d45e91

Specs: https://ezno.sharepoint.com/:w:/s/ProductTeam/Ef5tcyfbsotIuHTNPmmiO2gB9C4yAuMR1rmcn40BszwKrw?email=sylvain.guittard%40ez.no&e=P0WOQy
prototype: https://projects.invisionapp.com/d/main#/console/19764397/413426251/preview