Hello
Thank you for your query. My apologies, there is actually no way to use SP Page Builder within the SP LMS, but you can publish the SPPB module in your preferred module position for your desired pages.
Regarding SP LMS, you can check out the documentation and blog links below to get to know more about it :
https://www.joomshaper.com/documentation/joomla-extensions/sp-lms/creating-a-lesson
https://www.joomshaper.com/blog/sp-lms-3-4
And regarding using Page builder within SP LMS, we will definitely keep this in mind and convey the request to our Developer Team, for future.