Things and OmniFocus, and probably other apps, allow clickable links between most objects: areas (folders), projects, actions, built-in views, filtered views. They do not have the syntactic sugar that Obsidian has, which makes them more difficult to use. Furthermore, one can link to objects outside the apps; Bear is a popular choice. I’ve used this feature myself. I’ve seen many people write about the use of links, with some constructing very elaborate workflows. On the whole, I think most people do better by maintaining some degree of separation between reference and actionable material, as David Allen suggests. It may turn out that AI eventually sweeps all of these issues away, but not so far.