I'm collaborating on a sector map with someone and was looking for a program we could use to send ideas back and fourth something to plot single points and label them. Doesn't have to be fancy. All the free programs I've tried are mathematical graphs and require 2 or more points to plot anything.
I looked around for something like this too, but not much luck. You could do what I did, and just set up a google sheet (like excel spreadsheets) like a grid, you can even share with friends to collaborate. It's not ideal, but it's something!
