Custom application properties

Is it possible to create custom application properties ?
We need some validation based on the property value and the property value can be modified by the administrator of the application. for example if the ValidateDateOfBirth property is true then it should ask for birth certificate at the time of registration. Now we can implement that by adding a new property key in but not able to modify it from the application. We want it to be customized from Application Properties window from Administration.


Of course it is possible and highly recommended.
See documentation for how to do it: