Item pinning
Through the CMS you are able to pin certain items to front of a section. Because these pinned items exist on the section object and not the playlist object (meaning you can pin different items with the same playlist) you'll need to pass these to the playlists/{id} API.
Pinned ID's
The section object will contain a property called pinnedItems which will be an array of ID's (strings). These need to be passed into the pinnedItems parameter in the playlist call.
When this parameter is passed Backstage will automatically adjust it's base query to put these ID's to the front of the response. They will also ignore any sorting parameters.
It's important that the ID's are passed in exactly the same order as they're received in the section object. This will determine the order of the pins, which can be governed in the CMS.