Thanks for the suggestion @dill! We have had some team members experiment with this feature in the past and it is certainly on our list of features to implement...
We're definitely open to adding a jumping capability, and it's something we've heard for quite some time. Jumping gives us great fidgeting and expressiveness in virtual worlds. So, with that said, I'll also just provide a bit of background context as to why we haven't tackled this particular addition yet.
Our movement system in Hubs, rather than using a collision/physics-based approach, uses a navigation mesh ("navmesh"). This means that, when we publish a scene, there's a manual step where the scene creator adds an invisible item to specify "walkable" space, and we move the avatar based on that.
As I understand it, this makes for a more performant system of moving (because we aren't constantly checking for collisions) but it does make it harder to implement a "true" jump, because we don't have a system for, say, landing on an item that isn't part of the navmesh.
But, as Michael shared, there are some prototypes that we have that work around that within our existing system. We would love to collaborate with folks who have a deeper understanding of game physics to identify a solid roadmap for the physics component of Hubs, because that tends to be where the conversation heads when we talk through jumping. 🙂