I don't understand...
 

I've accessed the wiki several times and I don't understand how to use the Authoring Kit. I see the Sample Game System but I don't understand how to access something to create one of my own. I was hoping to use it to make Scion inside Hero Lab because the thread where a guy was doing that seems to have died, but I can't seem to understand how to even get started.

As well, is there an index of user created game systems or do I need to randomly wander the forums and hope to stumble on one?

The is a menu item , I don't have it in front of me, but it's something like copy game system or create new or something like that. You then edit the xml file in that newly created folder to implement you games features. It is a lot of work and the more complex the system, the more work it will be. The first thing you need to sit down and think REALLY hard about is your nouns, things like ability, skill, edge, weapon, etc. Do this before you start editing.. write these down and keep this list handy and go over then multiple times to make sure you are. It missing something.

It sounds like 'Scion' is based on World of Darkness/Exhalted.
As such, you may be able to copy the WoD system (like jfrazierjr suggests) and modify that to get closer to what you want than if you try to build it from scratch with the Authoring Kit.

I've found the create game system option, but it's greyed out. I've tried every game system and no matter what I do I don't have access to most of the develop menu.https://img00.deviantart.net/0469/i/...ee-dbqnqaa.jpg

At the very top of the menu, turn on "Enable Data File Debugging". That will allow you to start using the tools in this menu, as well as other tools like right-clicking picks to look at their fields, tags and script lists.

Did Matthias's advice help? He's pretty busy right now, with the release of Starfinder coming up, but I went through the Savage Worlds stuff recently myself, and I'm about 75% of the way through my own system. :) We all help each other out here.