To change the default key bindings, you can add a synfony configuration file in your project. The structure of the file should be like this:
pimcore_studio_backend:
user:
default_key_bindings:
save:
key: 'S'
action: save
ctrl: true
You can find the predefined key bindings here config/pimcore/user_key_binding.yaml
in the Studio Backend Bundle.