Kohn-Sham DFT does not give direct access to all quantities one may be interested in. For example, most energy eigenvalues of the Kohn-Sham states are not directly related to the real interacting many-electron system. For the prediction of optical properties one therefore often uses DFT codes in combination with software implementing the GW approximation (GWA) to many-body perturbation theory and optionally the Bethe-Salpeter equation (BSE) to describe excitons. Such software has to be adapted to the representation used in the DFT implementation. Both the GWA and the BSE have been formulated in the LAPW context and several implementations of such tools are in use. In other postprocessing situations it may be useful to project Kohn-Sham states onto Wannier functions. For the LAPW method such projections have also been implemented and are in common use.