Being able to click on an army icon in the status / summary panel (? Panel On the right in strategic map) is a nice and a convenient way to quickly move between your armies of interest. The problem is that by mid game you have amassed a lot of units that remain stationed (like administrators) in a city, all showing up in the list as a single unit in the order they were created/gifted. Most of these just become useless place holders taking up a lot of space and making it hard to find the army your interested in selecting.
Suggestion: Allow drag and drop so units can be relocated in the list; or, a check box (or something) to “Don’t display garrisoned units”