When adding a new Lesson "Content page", the "save page" button label wrongly says "Add a question page".
I suggest the following fix to display "Add a content page" when we are adding a Content page.
file mod/lesson/locallib.php line 738:

if ($this->qtype == LESSON_PAGE_BRANCHTABLE)

else

$this->add_action_buttons(get_string('cancel'), get_string($stradd, 'lesson'));