If you use text replacement shortcuts on iOS and your Mac, syncing has been unreliable as they’ve been using the deprecated iCloud Core Data, but that is soon changing. An Apple spokesperson confirmed to Daring Fireball text replacement syncing with CloudKit will be coming to iOS 11 and macOS 10.13 High Sierra users in the “next month or so.”
Here’s how Apple describes text replacements for macOS Sierra:
In many apps, you can automatically replace text and punctuation. For example, you can automatically replace a double-space with a period and a space, teh with the, or replace straight quotes with “curly” quotes (called smart quotes). You can also have Internet addresses (URLs) converted to clickable links (called smart links).
If you rely on text replacements, this should come as good news for you. You can learn how to create text replacements over here.