Relationships and Characters are the critical data for a World of Darkness Chronicle. They are the engine that makes the story run. But they are hard to keep track of at scale - Chronicles rapidly grow to dozens of SPCs when you've got a whole city to run.
I am a big proponent of Storyteller tools - I have a whole article on what I use. I started my most recent Chronicle with World Anvil, but I found keeping Storyteller Player Characters (SPCs) in World Anvil very difficult. The thing that matters most is the relationships between characters and that was hard to do in World Anvil, so I had to go looking for a new option.