Alright,
I was successful in adding the Lesson Topic Action/Trigger. Testing went very smoothly. This is what I changed:
badgeos-learndash.php
Added Lesson Topic Trigger to Action Hooks On Line 85
includes/rules-engine.php
Added Lesson Topic Action Hook (learndash_topic_completed) On Line 151
includes/steps-ui.php
Added Lesson Topic Trigger to Actions Dropdown List () On Lines 148 - 170
Added Lesson Topic Default Step Titles On Lines 287 - 299
Added Lesson Topic to Form Toggle One Lines 405, 424, 444 – 446, & 470 - 471
Pastebin is down at the moment, but if you'd like to download the files and use the code to update the plugin, here it is: