Hi Michael,
The @ sign is really only used for @rootid, those are object aliases for objects referenced within other objects in context of the current time - meaning for example the logged in user - who is logged in doing this operation right now... @root. I dont believe you can add additional ones. Spelcode are the methods by which service desk performs its functions (by definition). We do not support custom spelcode, but many customers do create their own. Its a proprietary language owned by CA, and solely used in CA Service Desk. There is limited information about it directly from CA as we do not have any documentation on using it. However, there are some folks here in the community that have shared their own documentation - you can take a look at this post: Where can I find Spel functions documentation? This post provides some great insight into what Spelcode is, how its used and what the capabilities are.
Please keep in mind that when you customize spelcode, CA Support cannot assist you in any way in creation of it, or troubleshooting any problems that occur due to using custom code. Additionally, you would be responsible to maintain that code through patches, upgrades etc.
Now for your original request, I would definitely recommend posting it as an "idea" here on the community. I think quite a few people would vote for it
Thanks,
Jon I.