For a real and complete slowmo you could slow down the update thread. You would also loose performance this way. Another trick could be simply slowing down all animations and player actions manually. I think the second way is the way to go since messing with the update timer may lead to side effects like hanging or crashing. There is an option in the physics engine to slow things down there afaik so all velocities will be slower as well. Just need an interface in Neo to access it 😀
If you want that feature very badly you can open an issue on GitHub so I don’t forget about it.