Thank you @Alfa1 for the clarification on this feature.
However, for the record and to anyone here who implied otherwise, XenForo does NOT provide a "featured threads" feature by default for any of its core content-types, nor does it provide any kind of generic system for featuring content. It is necessary for every add-on to design its own "featured content" system. This is added for resources in XenResources, and possibly also for media in XenMediaGallery.
That's why I suggested using feeds, because the feature already exists in VaultWiki since 4.0.0, was designed to basically do exactly what you are asking, and honestly it's not THAT more complicated than clicking a direct "feature" link. The only part that's missing from the OP is the option to have it as a sidebar block rather than a banner block.
1. Establish an empty "Featured Articles" feed on your wiki index or area of choice (this only needs to be done once).
2. In the article you want in the feed, go to Options > Promote on a Feed (feel free to change this text to "Feature this Article"). OR, if your wiki has the "Share This Page" sidebar block active, the "Promote" button is right there.
3. Select your "Features Articles" feed, and submit.
4. You're done already.
If this does not "feature" the articles on the index or area page, then there are bugs in the implementation.
Since there are no "built-in tools" in XenForo to do this already, this method is as valid as any other. The only improvements I can possibly see are:
- Have VaultWiki provide a featured feed by default as an index/area option (so an admin doesn't have to create it first).
- Have a shortcut to add an article to that feed (to skip the extra "Choose a feed" dialog).
- Improve the style of the featured feed for this purpose (I think it looks like a ticker box right now).
These changes would make "featuring" wiki content a little more straightforward, and more consistent in feel with the way it works in XenResources.