List of M2 Variables used in the source code

Can I get all the variables Membership 2 Pro variables used in the backend?

Here is an example: $member = MS_Factory::load( 'MS_Model_Member', $user_id );
Here's another one $membership_id = $subscription->membership_id;
Here is one I fetched from iDevAffiliates plugin: ms_invoice_paid

I need these variables to track my M2 sales and to insert the variables in that plugin settings: