In the lower-left part of the Playground there’s a right-facing blue arrow, looking like a “play” button.
Do a long click on this button and you will get two options: “Automatically Run” and “Manually Run”.
Choose the latter to put the Playground is manual mode and start/stop its execution yourself by clicking on this button.
You can also trigger the code execution by making a custom shortcut to the “Execute Playground” Editor menu command.
Go to Xcode > Preferences... then go to Key Bindings, scroll down to Editor Menu for Playground and add a new shortcut of your choice by double-clicking in the right column in front of the Execute Playground command.
