The functionality of the "left menu" in the lesson module is not very clear to new users. This could be easily fixed by updating the labels and descriptions around the "left menu"

Since the "left menu" is essentially a navigation block for the specific lesson activity, I think the text describing it should be updated to reflect that:

Current Strings:
$string['displayinleftmenu'] = 'Display in left menu?';
$string['displayleftif'] = 'Minimum grade to display menu';
$string['displayleftif_help'] = 'This setting determines whether a student must obtain a certain grade before viewing the left menu. This forces the student to go through the entire lesson on their first attempt, then after obtaining the required grade they can use the left menu for review.';
$string['displayleftmenu'] = 'Display left menu';
$string['displayleftmenu_help'] = 'If enabled, a list of pages is displayed.';

Suggested Improvements:
$string['displayinleftmenu'] = 'Display in the lesson navigation';
$string['displayleftif'] = 'Minimum grade to display lesson navigation';
$string['displayleftif_help'] = 'This setting determines whether a student must obtain a certain grade before viewing the lesson navigation. This forces the student to go through the entire lesson on their first attempt, then after obtaining the required grade they can use the lesson navigation for review.';
$string['displayleftmenu'] = 'Display the lesson navigation';
$string['displayleftmenu_help'] = 'If enabled, a block allowing users to navigate through the list of pages is displayed.';