DigitalSignal
Could be could the "Liberian"or the "Collector". Sith and Jedi come to him for knowledge of the past, and to learn forgot things. But also he has to be careful of those who want to take the knowledge he holds.
I agree with AgainBoin he should collect, record and invest in buisnesses to and collect Holocrons of sith and jedi true time. And sometimes show up to talk with Jedi and Sith. But also be recorded in they history as Shadow Master. But for now he should train. Please answer author to this comment what you think.
well the big blank you mentioned still has the first great schism, the pius dea crusades. He could atleast chronicle things and keep records of things long forgotten like the origins of the Je'daii, existence of the Bendu etc. Visit places like Rakata prime before they got eroded by time. Plenty to do, but yeah probably gonna be a lot of timeskips unless you gonna add a loooot of stuff.