I'm not able to sort by folder size. The option to "Keep folders sorted alphabetically" in folder options is disabled and I'm running DO 12.26 on Windows 10 Pro x64 with the latest updates. When I move my cursor over a folder it sorts that folder by size, but I would have to do that for every folder to accomplish this task.
Read here for an explanation and solution:
https://www.gpsoft.com.au/help/opus12/index.html#!Documents/Calculating_Folder_Sizes.htm
Thank you very much for your help. That explanation helps. I'm calculating folder sizes in DO now. Why is TreeSize able to calculate folder sizes so much faster?
It's probably not. I think it scans the drives in the background and stores the results in a database. Looping through folders and adding up file sizes seems like a rather simple algorithm with little potential for safe optimization.