steve's closure with peggy in endgame should've been a moment in the 1970 scene when he's in her office and watching her through the window busy at work. he sees/hears peggy's assistant or secretary come in, saying, "your husband called. he said the kids got in safely and are at the house now and can't wait to see you." (this is assuming the kids were born in the early 50s and are college-age/have moved out by this time) or something along those lines. or steve sees her husband himself (my man, sousa!) coming to visit her at work and saying the same thing in person. either way, these scenarios allow steve to see (even though he's probably heard her life story many times while visiting her) that a) peggy was thriving and successful at her job, b) she raised a family, and c) she moved on with her own life without steve. then as he realizes these things, steve lets a soft smile creep up onto his face and whispers "goodbye, peg" as he leaves. and that would've been it.