This is an attempt to make the city scroll bar on the left side of the screen somehow... useful.

On the top of the screen there would be several buttons, turning sorting and display on/off.
One button for each resource.

• City Name (normally, your cities aren't even sorted alphabetically, which is madness with 50+ cities)
• Level and Population  current / max
• City level (important for building booster improvements) and production of the selected produceable resource from material to mounts.
• Undeveloped resource tiles in zone of control
• Enemies in zone of control  (red number) or in sight but outside it (yellow number)

Clicking one of them would display the one selected stat (such as the name!) to the right of the city and sort the list by it.
So you could, for instance, bring all metal producing cities to the top when you have researched smelters and want to build them where they do something useful.

I'm sure there are other useful sorting criteria but those would already go a long way.