Dear Rudolf, indeed, manybody expectation values involving thermal averages over the occupied states are only available in tkwant by now. The "voltag_raise" tutorial you mentioned is a good reference, just make sure that you stick with the new version (tkwant's API has slightly changed): https://kwant-project.org/extensions/tkwant/tutorial/AC_josephson_without_su... For spin currents, it should work similar to the kwant operator tutorial you mention, with an operator kwant.operator.Current(syst, sigma_u) and sigma_u = ((1,0),(0,0)) for the upp current, respectively sigma_d = ((0,0),(0,1)) for the down current. Best, Thomas