npub15xlf045s9sutk2chghqq5w6lfsmdkl2mymdtj825pxslfs3s74xqw7dj0q (npub15xl…dj0q) it depends on context.
If we are talking about how to use it in a book, then: "nota al margen"
If we are talking about a conversation between two or more people, then I'd go with "dicho sea de paso" which is more akind to a "oh, and by the way".
If you can provide me the right context, I can give the precise translation 👍