I originally made this to get the sum of the duration_connected property, although it turns out it's only been tracking the event since June of last year, which was disappointing. Feel free to try it out, although there's not much to it since I was just trying to get a single property.
Note: This requires the /analytics folder in your Discord package to be present, which will only be the case if you have "Use data to improve Discord" toggled on.
This is a fork of Androz2091's project, just rewritten in React and modified to process the analytics.json file line by line so I could get sums.