Is there a way via Garmin / Strava / Etc to pull in weight training data to the calendar?
Not now. We will get runs integrated at some point per the road map. I am guessing strength would be part of that too, but who knows for sure?
Maybe a possibility via third party?
Edit: Smart-Scale-Sync product only syncs from Withings to Garmin Connect, or from Withings to TrainerRoad.