The patch for T228210: Homepage: Allow experienced users to claim mentees introduces a notification that says "Say hi to your (new) mentor!". It might be interesting to experiment with showing this notification after a certain period of time has elapsed (30 minutes?) or number of page views as a way to engage with a new editor. The notification drops you straight onto a user talk page which is probably a bit overwhelming, but if the GrowthExperiments-Help panel experiment is open (or if you're on mobile) then you get some guidance on how to move forward.