Answer:
RSTAB 8 and RFEM 5 are two separate product groups, although the features of RSTAB are also completely integrated in RFEM. All RSTAB add-on modules are also available for RFEM. Some program parts are extended in the RFEM product group for surface and solid elements.
The only exception is the SUPER‑EK add-on module. This add-on module is only available for RSTAB.