Project custom field values in search API call

I came across this thread after reading through Custom Fields At A Project Level - Not Task - #31 by Kiltie_Colavita . The issue we are facing, which seems to remain an open question, is how do we “utilize” the custom fields at the Project Level? Within Asana I do not see how to sort/filter/search projects that have a project-level-custom-field tag – and I am not having any luck within the API in retrieving custom fields at the Project Level. These are “visible” within a portfolio and when opening a project directly by viewing Project Details – however is there a way to retrieve all the data shown within Project Details via API to build out the community requested functionality if not available within Asana e.g. the project level custom fields etc.? See attached.