Good thoughts.
If it helps ... click in a number box, type in the number you want, press Ctrl-A, Ctrl-C.
Then, next time you come to the same box, click in it to enter a number, then press Ctrl-V.
I use this frequently when yielding. e.g. I know the number of troops I need to entirely capture a 1M stone or lumber camp. When sending out 14 marches, retyping or selecting things and dragging them gets old - to your point.
The same idea works for sending the same message to multiple people. Type your message, Ctrl-A, Ctrl-C, send, pick next recipient, Ctrl-V, repeat.
Cut and paste does not work between inside and out of the browser, as you likely know. But it does work within the browser - something easily lost sight of.
Cheers.
GL&HF!