You can add items to a user’s Reading List in Safari by calling the addItem method on the SSReadingList singleton.

let readingList = SSReadingList.default()
readingList?.addItem(with: yourURL, title: "optional title", previewText: "optional preview text")

The default Reading List can be nil if access to the Reading List is not permitted.

Additionally you can check if the Reading List supports a URL by calling supportsURL.

SSReadingList.default().supportsURL(URL(string: "<https://example.com>")!)

This will return either true or false indicating if the given URL is supported by Safari Reading List. Use this for example to determine whether to show a button to add a URL to the Reading List.