On macOS it is possible to open more than one options dialog.

On other platforms this is not possible, since the dialog is modal and blocks access to the main window, which also disables access to the menu.

On macOS:

a) The dialog actually is not created modal (not sure why)

b) Even if it is made modal you can still open another dialog, since opening this dialog is a standard action in macOS global menu

Having multiple dialogs open can result in unintentional overwriting of settings.