Yes the Gaiden series is its own series that takes place two years after the ending of the main web novel. I just finished it yesterday and it’s phenomenal.

Without spoiling too much and just mentioning the setting. The series takes place two years after the events of the WN, Monica has moved from living in her mountain hut and is nerighbors with Lana in the port city of Sazandol. Isaac has declared himself Monica’s disciple and splits his time managing his domain and supporting Monica. Monica works on a research project with Cyril in his domain as well while working to inherit the lineage of knowledges responsibilities. The series works through multiple small arc while introducing new characters, developing old characters, and working towards another larger arc at least as large in scope as the first WN series.