Idea Summary
Popups in APEX can close only by clicking the Close/Cancel/X buttons or Esc key. Provide a property to be able to close them by simply clicking outside the popup for a better UX (because the user's hand is already on the mouse).

Use Case
Modern web apps have their popups close by clicking outside the popup for a better UX and predictable behavior. Popups like (?) Help Text popup could be closed safely without any data loss by clicking outside the popup region. Even dialogs could be closed by clicking outside them if there are no pending changes on them. Having to click the X button to close gives a bad UX.

Preferred Solution (Optional)
Provide an optional switch property to close by clicking outside the popup/dialog.