Hi Paul

It is possible to create custom profile fields for users. These fields can be used with  audience rules to select mentees and mentors of similar background.

Use the audience to enrol the users in the course and then use the audience sync enrolment method in the course to assign the user to groups.

Use separate groups for the assessment activity in the course so the mentor is only able to see and mark their own mentees .

Hopefully this gives you some ideas on how Totara could be used for this function.

regards