What Additional Evidence can I provide apart from a Letter of Recommendation as a proof of Mentoring

Hello great Talent,

Congratulations to everyone here that have been endorsed for this visa. Please, I want to ask, what could be an additional proof that shows that I mentored during my University days. I am asking this because the recent changes states that Letter of Recommendation alone evidencing this alone can no longer be accepted. Please, I would welcome your advise and suggestion. I am about to apply for the endorsement for the second time. Please kindly help me.

Is it possible to share the changes about the Letter of Recommendation?

Here is the evidence above