I wanted to change the text of the EMAIL_ROLE_ASSIGNMENT_BODY found inside of the languages in admin.
There were a couple of variables that I was hoping to use from DNN as there is a [Custom:0], [Custom:1], [Custom:2], and [Custom:3].
I assumed that there was an easy way to do this, but through all of my searching, I was unable to change what the Custom token values were.
I know that it's not the same from piece of language to piece of language as [Custom:0] references the date in some and Name of Role in others.

Where is it that the [Custom:#] tokens are populated and how can I either edit the value, change the reference, or add another Custom token (i.e. [Custom:4])?

If I was to make changes to the core, where would I find these values to change?