There's this Meta post, that gets featured now and then, with a list of canonical questions:
¿Qué preguntas canónicas tenemos? What are the canonical answers we've discovered over the years?
Desktop users can see it in the side panel of the Main page when it is featured. Sadly, it seems like side toolbars are not visible for mobile users.
Another way of linking to canonical questions is by properly marking duplicates, i.e. if a new question is a duplicate but there're several questions we could pick as target, we should always try to pick the canonical one if there's one (and improve it and mark the others as duplicates too, when needed).
Some other sites promote using each tag's wiki to link to related canonical questions, which would be a good idea if users actually read the tag wikis (I doubt it).
Beyond that... there's little left we can do. As a Beta site we don't get to have custom sidebars like those in Photography.SE (we don't, do we?), which could be used for this, and I cannot think of anything else regarding "passive" promotion of canonical questions.
Of course, we can always do some "active" promotion by linking the canonical questions in our own questions, answers and comments.