Usually when I think about clicks, it has to do with marketing on the internet. But I'm seeing places in the physical world that would benefit by adding a click to improve functionality.
Our camping stove has a very high powered output. It seems designed to get water boiling as fast as possible. But that makes it hard to cook with any subtly. And by subtly I mean medium heat. Once you turn the knob and light the burner, it is difficult to adjust the flame. There is little friction to find and hold the knob in a less than full power setting. But adding a click to the knob would allow you to maintain a lower flame.
Our AirBnB cottage has sliding barn doors in the bedroom and bathroom doorways. These slide shut easily, again, without friction. If you close the door too hard it will bounce open. Even without a bounce but a gentle close, the door will slowly open. This is not the preferred way a door should work, especially in a bathroom. A simple notch, or click, can hold the door in place once it is closed. This seems like an easy solution to improve this door's functionality.