I am currently trying to set up a very basic blog using Composer. I am using the built-in property of Page Location as one of the options (see image below)

https://www.screencast.com/t/mkGqRFXII...

I would like to create a custom form for editing the Page Location, which I believe would be done using a composer.php file, but I don't know how to do that for a built-in property.

I have tried to search for this, but haven't found any answers, so I figured I'd post here.

How would I go about doing this?