Yo,
I just thought of something that could be really useful.
In addition to requiring the previous node to be unlocked in order to access the connected ones, it could be great to have an optional requirement based on a Switch being ON. This would allow the creation of perks that remain locked until the player unlocks them through gameplay conditions , for example, reaching a certain point in the story.
I think this would give developers much more control over progression and would be useful in many different scenarios. Let me know what you think when you have time.