I think you may have misunderstood, by open a folder, they meant open a folder of buttons on the stream deck, allowing you to press a button to completely change which buttons are displayed on the screen.
Is the goal to be able to have multiple sets of key mappings depending on which "folder" is open, sort of how you might describe "profiles"?
If so you can do that with numpad re-mappings too. You could have 17 specific key mappings depending on which app is in focus or you can arbitrarily activate a different specific set of mappings.
It's not going to be as intuitive since there's no visual icon to display but the functionality is there. AutoHotKey could also make it easy to show which "folder" is active by showing a little tooltip when you switch folders.
It sounds like the real appeal to it is the visual icons but the trade off is needing more desk space and reaching for buttons that are not on your main keyboard (+$125 to buy it).
