‘Text Replacement’ already has some built-in shortcuts such as ‘omw’ which when typed becomes ‘On My Way’ and ‘;tel’ which is replaced by your registered phone number.
Apple also provides ‘Text Replacements’ for hard to find symbols such as (c) becoming the copyright symbol © and 1/2 becoming ½.
Note: Any ‘Text Replacements’ you create will be synced across all devices that use the same iCloud ID.
When happy with your settings, either tap the back button in the top left of the screen or press your device’s ‘Home’ button to return to the home screen.