  For a certain class of open quantum systems there exists a dynamical symmetry
which connects different time-evolved density matrices. We show how to use this
symmetry for dynamics in the Liouville space with time-dependent parameters.
This allows us to introduce a concept of generalized coherent states (e.g.
density matrices) in the Liouville space. Dynamics of this class of density
matrices is characterized by robustness with respect to any time-dependent
perturbations of the couplings. We study their dynamical context while focusing
on common physical situations corresponding to compact and non-compact
symmetries.
