Customizing the Galaxy Watch 4 Buttons for your own needs, including fast app switching

The Samsung Galaxy Watch 4 comes with two prominent side buttons that can be easily configured to your tastes. These are the Home Button and the Back button.

Head over to the Settings app on the watch and choose Advanced features > Customize Keys.

Here you can set up the buttons for specific actions.
For the Home key, we love the Double press option that allows quick app switching!
- We recommend choosing “Go to the most recent app,” but you can also set up your double-tap to take you to a specific and frequently used app.
Press and hold options include accessing Bixby or Power off.
For the back button, choose between going to the previous screen or show recent apps in an app switcher environment.

Most folks customize the Home button key and use the back button to go back to one screen with its default behavior.

Source : myhealthyapple.com