How to search by tag(s)?

How To
1

… across all the notes, be they in agenda or not.

Tags of a header or of a document.

Why isn’t there a simple, definitive answer? Isn’t there a built-in functionality for such a basic and effencial activity? The answers I’ve found thus far have been “install this, then set up that, then add that hotkey, type that command first, and then…”. Or “add that itnto agenda first and then”.

Why add anything into agenda, even temporarily? For what? Will I have to add all the notes into agenda any time I need to search by tags? Nonesense.

2 
  ;; If you're using a vertical completion framework, you might want a more informative completion interface
  (setq org-roam-node-display-template (concat "${title:*} " (propertize "${tags:10}" 'face 'org-tag)))
3

How will that search by tags?

4

The usual way: org-roam-node-find or org-roam-capture.

5

How will that search by tags?

6

Can you show us how it does not work for you on your end? Perhaps with a screenshot or two with your description?

7

@x00a you can do the usual org-roam-node-find or org-roam-capture as @nobiot said and then start typing the tag, for example “#project”