invisibleknob
nounUK /ɪnˈvɪzəbəl nɒb/
US /ɪnˈvɪzəbəl nɑːb/
A knob you cannot see.
She turned the invisible knob and the secret door opened.
OTHER MEANINGS
2. A control that is hard to find or notice.
The settings menu is an invisible knob that few users ever discover.
3. A hidden or imaginary control in a game or story.
The wizard's tower had an invisible knob that only appeared at midnight.
4. A subtle factor that quietly changes how something works.
Interest rates act like an invisible knob on the economy.