Great work! I look forward to trying this out. Looking at the docs a little more closely I see
NOTA : metadata is not (yet?) available via paperUI. Either you create your items via “.items” files, or you can:
Besides the misspelling of “NOTE” (“Hey pot, you’re black”), I think I can answer this. Metadata is definitely not available in PaperUI and will not be available in PaperUI. It should be available in the replacement to PaperUI. There are a couple of REST API end points available to add/remove metadata on Items so it is possible to add the info just like we used to using the REST API Docs to add tags too. Just use PUT /items/{itemname}/metadata/{namespace} instead of PUT /items/{itemname}/tags/{tag}.
Unfortunately there isn’t really a REST API endpoint to easily get all the metadata settings on a given Item, but you can use the GET /items to only get those Items with a specific metadata setting.
Metadata is available in Scripted Automation so you can get and set them from Python/JavaScript/Groovy Rules if you have a reason to, so you could set these through Rules as well if that is easier for you. It is not available from Rules DSL though. See Design Pattern: Using Item Metadata as an Alternative to Several DPs for examples of that.