A toggle in the Feature Toggles administration interface allows ADMIN and PORTAL_ADMIN users to enable or disable My searches:
The My searches feature is disabled by default.
When enabling the My searches feature for the first time, all of the user's Scopes and Alerts are converted and remain available. However, if an administrator chooses to disable My searches after having previously enabled it (to go back to using Scopes and Alerts, for example), some user assets may be lost in the process.