That plugin is pretty minimal and doesn’t make a lot of sense, really. The library it uses “sortable.js” is actually pretty good (and I use it myself in my Floppy plugin), but all the “save” feature does is save the order of the sorted items to localStorage. (This is a feature of the library that I actually find somewhat silly.)
But this isn’t really useful in any meaningful way in Bubble. Because what you really want to do is have access to the reordered items back in Bubble. This is a much bigger challenge, but one that I’ve solved in my Floppy plugin.
Floppy is a plugin that’s mostly for browser storage (and handles pretty much any Bubble data type), but it also has advanced list manipulation features, including the ability to make an RG sortable while also getting the new order of the items back via the plugin.
Most recent video about this feature is here:
The latest versions also allow drag/drop between RGs (simply by giving them the same “drag group” name in the main interface), but I’ve not finished a video about that.
Anyway, sorry your previous purchase of somebody else’s plugin wasn’t actually useful, but you may want to watch my video(s) about Floppy and test it out should it look promising. The Floppy plugin itself contains an ever-growing number of plugins, and not just the Floppy element itself.