I have an Excel Spreadsheet Template always on a second monitor that provides me with: plan, designs, missile stockpile calculator, terraforming tool, logistic tool, ground unit templetes and formations, memory wall etc.
Even if there was a inbuilt calculator/note tool I wouldnt use it to be honest.
I do understand why the request though.
Aurora should have into the basic requirements 2 monitors or even better 3, like I have. With one monitor it's mostly unplayable unless you are prepared of jumping from a window to another.