Anyone figured out how to do that most efficiently? You can't have two "old" co-existign at the same time? I'm using the rename method but struggle each time Which one is better to rename, the old-old or the new-old?

This should work in PowerShell on Windows or on other systems with a normal shell as long as your downloads folder is called Downloads and you don’t have a folder called old next to Downloads:

mv Downloads old && mkdir Downloads && mv old Downloads

This is assuming there aren’t any special permissions/attributes on Downloads

Some of them seem to have weird things where renaming a directory keeps it still the "downloads" directory - I prefer moving the contents of downloads instead.

I'm not sure how I do it since I do it differently each time, but I do see some called "older" so I think I rename the old one then move.

This is me :) … it’s currently “Downloads/files/misc/old/older files/to be deleted”.

Every week I select all in my Downloads folder and delete.