With the new, to me coming from OH2 anyway, tags directory, the included default readme.txt is
Your semantic tag definitions go here.
All semantic tag files have to have the “.yaml” file extension and must follow a special syntax.Check out the openHAB documentation for more details:
https://www.openhab.org/docs/configuration/semantictags.html
But trying to find out about these the link only goes 404.
Also searching for semantic tags doesn’t help much, nor is there an obvious Sematic Tags section under Configuration Guide.
Not sure if and when I’ll ever need them, but would be nice to be able to easily look up more information about this new directory and its possible content.