So obviously, all I’m about to say is just connected to a tiny easter egg the writers of Runaways put in their show, and it was never meant to be part of a conscient continuity. But if it was…
I’m also using the timeline on the MCU wiki, which may not be totally accurate, but is close enough.
In Agents of S.H.I.E.L.D. 4x22, there is the final fight against AIDA, which takes place on May 12th, 2017. Then, Coulson hands Robbie the Darkhold, and he takes it to another world, some kind of mystical plane, to take it somewhere safe (!), then fight some mystical war.
Then, later, on Runaways 3x07, we see the Darkhold again, in the real world, and definitely not somewhere safe, since it is in Morgan’s hands, who claims it is her spellbook.
Now, assuming she had it since her return on Earth and found it in the Dark Dimension (or else Robbie failed to keep it safe earlier than I thought), she possesses the Darkhold’s powers for at least since February 19th, 2018, less than a year after Robbie was tasked to protect it.
So, where the hell is Robbie ? Knowing Morgan’s sick mind and her having absolutely no problem to kill, well… She is very powerful. She could have overpowered the Ghost Rider. Robbie might be dead.