WCAG success criterion: "All functionalities of the content are operable through a keyboard interface without requiring a specific timing of individual keystrokes, except when the underlying keystrokes, requires inputs that are dependent on the path of the user's movement and not just the endpoints."

As a user who relies on keyboard control, I would like the calendar list and subscriptions to be able to be enabled/disabled with the keyboard.

Assistive hardware, such as that used by motor-impaired users, often uses the keyboard interface. The operation of a website should be device-independent and accessible with both the mouse and the keyboard.
The control element marked in red can be controlled via keyboard, but not activated. Motor-impaired users, who are dependent on keyboard operability thus do not have access to the offered function.

It is possible to disable/enable the display of the respective calendar by pressing the Enter key when controlling and selecting the FlipFlop switches in the calendar list and subscriptions.