To use:

1. Load the excel file (and enable the macros)
2. Click the only button on the form (called Generate To Clipboard), this puts the new map in the clipboard
3. Go into your GalaxyForge directory and make a new text file; renaming it as .galaxy instead of .txt
4. Paste into that text file
5. Save / close the .galaxy file
6. Load up the map in Sins!

I have hard coded "Is First Capital Ship Free" as false.  But you can change it in the worksheet called galaxyTop (see the red text therein).

There are numerous ways to customize the random galaxy; the size; the number of planets; the composition of planets; then number of interstar wormholes, etc. I tried to explain this in the <-- notes in the file.

The planetCountChance might be confusing to use.  I have 9 as the top row; and if you change the % from 0% to 100% then every star created will contain 9 planets.  If you change it, intead, to 10% and then change the second row to 100%; imagine rolling a dice for every star.  If the dice roll is 10% or less then the star will get 9 planets, otherwise it will get 8 planets.

The Planets section might also be confusing unless you know how sins currently randomizes planets.  The GalaxyGen that I uploaded contains 34 items in the Planets list.  If you were to change it to just one item, Asteroid, then every single planetoid will be an asteroid.  If you put two items in the list, Asteroid and Ice, then half of the planets will be Asteroids and the other half Ice.  If you put Asteroid in the list twice, and put Volcanic in the list once; then 66% of planets will be asteroids; and the other 33% volcanic.
Maps do not have much replayability.  For this reason, I generate a new map every time I play sins .  All it takes is one click and then save the text into a .galaxy file