Hi there,
At the moment, we can’t save a character sheet without completing all the creation steps. This limits game styles where amnesia or uncovering your character’s skills is the driving force behind the game progression.
It would be great if we could proceed to saving and sharing without having necessarily completed all stages of character creation.
Unless I’m misunderstanding something you can theoretically do this as it currently stands. You can manually click between any section within the builder and you can always click out of the builder and into the character sheet to share at any time.
The way I assume it would work is that you’d fill out the information you know for certain about your character, then click out to the character sheet, share the character to your GM, and then let them make a copy of the character to finish out the specifics.
I didn’t see that on the left hand panel, as I’ve been looking at the buttons in the character creator in the middle panel. Thanks for pointing out my oversight! 
I guess for this style of game, a Storyteller would need to have two copies of the chronicle - one with the blank sheets that the player’s have access to, and on with the completed character sheets to reveal to the players…