One way to implement tagging is by adding Multi-select property called “Tags” and use that. Just remember to unlock the main database first. One downside of such a tagging setup is that those tags would apply to the entire note.
However, what I'd suggest here is utilizing the relation to the 🗃 Areas/Resources database. In my setup, I use Resources as basically a master tags database, where I can see individual notes connected to that tag. Here's an example:
This might also be a useful way of doing per-block tags (a piece of text, and other page content). Sadly, there isn't a nice “native” solution for that in Notion at this moment. What I'd do here is do an @-mention to the Resource page containing that tag:
This way, all block mentions will get displayed nicely in a separated section: