English abbreviation for: added by redaction

In English, you would see such material in brackets, such as "Rodger [her dog] died..."

In some instances, you might see "Rodger [her dog --Ed.] died..." to make it plain that the editor added the explanation.

I'm not familiar with a word English would apply here. Usually, text inserted by an editor is set apart with square brackets, while stylistic changes are explained parenthetically. Longer explanatory text may be "signed" by the editor as well to clarify that it is not the product of the original author.

So, for the example given, I would say

"Karen was very sad when [her dog] Rodger died …"

"Karen was very sad when Rodger died …" … (emphasis added)

"Karen was very sad when Rodger died …" Rodger was Karen's beloved dog– Ed.