We have a Windows desktop program where from the Main screen users open a settings dialog (Dialog A). On this dialog they can edit various settings and once finished, they can click OK and changes are saved and the dialog closes. Or they can click Cancel and the dialog closes without saving.

Additionally, from Dialog A, some settings open a 2nd dialog (Dialog B) for editing that particular setting. As before, Dialog B also has an OK and Cancel button. 

If users edit a value in Dialog B and click OK, the change made is saved and they return to the still open Dialog A. But my question is, what happens if they now click Cancel in Dialog A? Should the changes made in Dialog B also be cancelled or should they remain applied?
[![Explanatory diagram](https://i.stack.imgur.com/CqjWU.png)](https://i.stack.imgur.com/CqjWU.png)