She never fought much on Hart to Hart. Disappointing. Back then I would have enjoyed seeing Heather Thomas from Fall Guy do a guest shot on H2H and totally dominate Stephanie in the last episode of the series. And as Steph is lying on her back sobbing and holding her aching tummy, Heather gives her husband a big kiss and tells her she's the new Mrs. Hart.
I'm going to disagree with you here! In Hart to Hart, Jennifer got into several brief fights, usually struggling with a villainess for possession of a gun. And she was usually victorious, e.g. in "Max's Waltz", "Ex-Wives can be Murder", "A Lighter Hart", "Hartland Express", "The Dog Who Knew Too Much" , "A Couple of Harts", "Vintage Harts" and a few others. Most were very brief, but she almost always won, e.g. here:
https://www.youtube.com/watch?v=6Pjd2zTW4vs&ab_channel=KenBarrow