4
A list of global Smarty tags
can be found here. These tags are to be used in templates and themes, they won't work (as far as I know) in the text editors when you post something.
Apart from the global tags there are also module specific tags. The best way to see which tags are available is as said above, by activating the Smarty debug and seeing a list of available tags for each page.
The codes you found in the admin section are specific to the mail module - I don't think they work as global tags, though I could be wrong. There are only 5 that I can find;
{X_UNAME} user name
{X_UID} user id
{X_UEMAIL} user email
{X_UNAME} user name
{X_UACTLINK} url link to activation key for given user
Hope this is the information you're looking for.
Rowd