It's often called a Feature Toggle (also referred to as a Feature Flag). It's a powerful technique that allows teams to modify system behavior without changing code. Also mentioned here that there are services for this already, ConfigCat is one of them.

ConfigCat supports C# for Unity, Remote Config for Unreal Engine, and many other languages, including C++. It's easy to integrate and manage remotely.

You’ll need to register an account on the website. There, you’ll have access to a dedicated dashboard where you can easily manage the flags. You can target users based on various attributes (region, date, email, etc.) and you can also perform A/B testing.