On the bottom of the "normal" screen there are many buttons in a row. The one furthest to the right is the design ships button. Toggle the next one to the left just beside it - I think that's the one - it has a lightning bolt? That will take you to another screen which - IIRC - begins with what gov't you have, what party you have and some third thing.
Along the top row of that new screen are several choice buttons. One button takes you to timeline charts. Another of those button takes you to the screen that shows your progress towards the various victories, like how many techs left to research for the tech victory, how much influence you have compared to the 75% needed for an Influence victory, how many alliances you still need, and how many empires you have still to conquer to win a conquest voctory.
However, among those buttons on that top row is "colonies" or a similar name.
Toggle the "colonies" button and it will present all you all your colonies in a spreadsheet alphabetically top to bottom. Each colony will have the table info of the column headers, which include mil production, social production, research, and $. Also, it will show what is being built - both ship and improvement. It shows the total number of improvement slots on each planet and how many remain unfilled. It shows the population and if the planet has at least one ship in orbit.
I cannot imagine trying to manage an empire with more than a dozen or two planets w/o this screen!
The "ship in orbit" is itself huge, as one step when the time of war approaches is to ensure each planet has at least one ship in orbit to deny those early unsupported invasions. W/o it, I find it easy on a large map to miss that one or more planets in my far-flung empire has no shield displayed on the galaxy map.
One of my favorite "tricks" or self-aids is to rename planets, in part because of this spreadsheet. For example, when I get a 53% "Starship Bonus" planet, I rename it 53% Ship Bonus. The # in the first character puts that planet ahead of all ones starting with letters. Thus, on this spreadsheet, it puts it on top of the page. That allows me to ensure I always have warships in production on those planets once I get them developed.