At some point in time, it will be necessary to work with a digital twin of Kayra to simulate all sorts of movements, weight distribution and possibly power. Also during the design process it would speed up the fitting of two parts.
I asked the reddit community about which software to use:
pyBullet is a simulation software that allows for importing the STL files you use for printing, it also runs in Python which is pretty cool. I think this has been around for a long time, it is not specifically developed for robotics, but rather a physics simulation.
Gazebo is another simulation software that also connects to ROS (Robot Operating System) and has been developed specifically with robotics in mind.
MuJoCo (Multi-Joint dynamics with Contact) is a third simulation software also for robotics. It seems that this has been developed from the ground up for robotics, the company behind it has been acquired by DeepMind and the software has been open-sourced.