As far as I know you can’t really do this with Magic Fields and I’ve been using it a very long time… one work around – you could create a new CPT select the quantity checkbox so it’s not duplicatable, and then create your “page” as a CPT with the custom fields you need… but then you’d have to incorporate this CPT into your page query and it will take some finagling in the theme files to make everything work. Not ideal at all.
You CAN do this with just Advanced Custom Fields. When you create a field it will let you select a specific page the field is associated with and then will only appear for just that page.
If you need CPTs, I can probably point you in the direction of some code to add to your functions.php to create them manually and then just use ACF. If you let me know a little more about what you are trying to accomplish and how your site is structured, I’d be happy to provide some more specific insight.
