SwiftKey does not have a dedicated minimize keyboard button. Instead, if you slide a finger down the keys from top to bottom, SwiftKey is minimized. Alternatively, pressing your phone’s back key will minimize SwiftKey.
Please note that if SwiftKey Flow is enabled, you can't slide down the keys to minimize the keyboard. When using SwiftKey Flow, please press the back button on your device to minimize the keyboard.
This gesture is not available for tablet or large screen devices, but using the back button on your device will still work to minimize the keyboard.
See the how-to video below:
Video captions are available here.