What is 'decommissioned'? Is it possible to mothball ships?
I have 3 classifications to help me in indentifying if I need to refit, rebuild or produce a new ship.
ACTIVE is a design which most likely have the technology ideal for the task without the need of an upgrade or simply the best technology is already installed.
OBSOLETE: is a design which has been surpassed by a better tech or there is simply no need for such ship as another may have taken over that role.
DECOMMISSIONED: is a ship which has reached its natural development and will not be produced anymore but still be used until declared obsolete.
By looking at my main screen I know immediately if I need to do something on my fleets in these terms.
The other info help me to identify if the range I am operating suits the purpose etc.
As statistics are dynamic by hiding a column on the main sheet I can take out what I don't need from the graph so I look at what I need rather than the whole picture.
This should also answer the question how I remember to upgrade techs etc.
Regarding other stuff I also use the map a lot using notes and labels. That again you can partially see in my latest aar update.
If used properly the galaxy map is a huge tool. I wish there were more options in it. I have tried to replicate it using world anvil and I must say, some integrations were amazing, only problem is maintenance to keep all up to date. If Steve is reading he may look into it?