Function mark_dialog_accept_on_default_click 

pub fn mark_dialog_accept_on_default_click(
    clicks: MessageReader<'_, '_, ClickEvent>,
    defaults: Query<'_, '_, (), With<DefaultButton>>,
    parents: Query<'_, '_, &ChildOf>,
    sessions: Query<'_, '_, &mut DialogSession, With<DialogMarker>>,
)

A direct click on an explicitly-marked DefaultButton inside an open dialog resolves that dialog’s eventual close as accepted. Text-child hit-shadowing is handled with the same ancestor walk the control dispatchers use.