@adrianCTOBelong, you can use either my Floppy or List Shifter plugins (both of which are found in the Floppy plugin collection) (forum thread) to create and manage lists that contain duplicate items, as mentioned in the thread that you linked.
Floppy was temporarily unavailable while I migrated some of its server-side actions to the new server-side plugin API, but it’s back in the marketplace and installable once again.
Using Floppy’s “RAM List” feature you can add duplicate items to a list and it supports all Bubble data types, including Things. The List Shifter element also has a similar feature (using “Custom List”) but it’s not as user-friendly as Floppy’s RAM List-related actions.
On the server-side, my plugins such as List Popper and List Pusher also enable/support lists with duplicates in them. (Those plugins are available in the List Popper & Friends plugin, which is free, but again they are specifically for backend operations.)