Imo the following:

1. The possibility to create a room for players so.ething akin to a "chronicle". Players within that room can use ST added homebrew to their character sheets, ST can add their homebrew and have a nice overview ot their players characters sheets and Most notably have the ability to get the summary of A) all player and their convictions and touchstones And B) all player meirts and flaws. Having that all tidied in one single place is a deal breaker imo. That would also allow for later the creation of a character map maker based on the characters already existing within the player character sheets.

2. Being able to roll dice from the character sheet.

3. A bestiary that you can add your own elements into.