Hello @jake_eason.773422 ,
"... I can arrive at Chittorgarh station, drop my bag at their left luggage, and pick it back up later that day for my onward journey (coming from Bundi AM, going to Udaipur PM). Anyone done this and know for certain it's an option?"
Yes, train station in India have "CLOAK ROOMS" - which are for left luggage safe keeping. They charge a modest fee of Rupees10 for 24hrs and are open 24 hrs (ask for timings or other enquiries if at a small station).
For safety, ensure your bags are locked and your bags need to be locked or chained properly to be submitted in the Cloak Rooms. Also, you need either an arrival or departure ticket for that station to use the cloak room.