by the way; incidentally; while I'm at it
Used when adding a related remark or request while already doing something else; similar to 'by the way' but with a nuance of taking advantage of the current situation.
By the way, I'll also send you the materials for tomorrow's meeting.
買い物に行くなら、ついでながら牛乳も買ってきて。
If you're going shopping, while you're at it, please pick up some milk too.