As of now the Wiki has 3 columns: "XCOM 2", "Other games", and "Universe".

The Navigation Bar allows to utilize up to 4 columns, meaning that 3 primary games can have their own column entries, whereas the 4th column could include a left-over game (Bureau), XCOM universe, and community links. Alternatively, all 4 games can have their own column each, while "universe" and community links would be placed to the right-side column of the main page.

If you would like to take part in forming of the revamped navigation bar, look at https://xcom.fandom.com/wiki/MediaWiki:Wiki-navigation to see how the structure works. After that you can create the per-formatted draft in your sandbox and post a link to it here. Note that each column can have up to 4 hierarchy levels, the title of the column being the level 1 level.

At the moment I am inclined to use the 3-game column variant till interested and active editors appear.