Understanding the purpose will help. It’s for posting or sending message or comment clips in one tap. So if there are things you say or anything you use a lot like links, quotes, symbols like the ¢ or ⓒ and etc you can do it on a tap. Here’s a link I use. I do it in one tap.
Or a tip:
My Wife and I share the same iTunes ID. That way we share purchases. The ID is mine. But she has her own iCloud, iMessage and Facetime ID’s. No issues this way.
Let’s look at the keyboard itself.
This is my set up.
Here’s in the App.