[Question] Checkbox

[Freire]

I want to make a checkbox in a program to act like the checkbox in the Symb view of the Function app.

There is a gap to write down your function and as soon as you write it down the checkbox gets checked, the opposite happens if you delete the function.
I find it to be a very good implementation and would like the same behavior on my program.
I tried some combinations, but I didn't figure out. How to change a checkbox inside an Input in runtime? Is there another way of input that could change in runtime?