Answer:
The reference system can be changed both in the graphical display in the Project navigator (see Image 01) or in the tabular results in the add-on module (Image 02).
Image 03 shows the different deformations of a structural system. On both sides, Construction Stages 2 to 4 are displayed from top to bottom, referring to the undeformed system (initial state) on the left and to the respective construction stage on the right.