In the KSP 7.8 Reference Manual there's a mistake on pages 184, 186 and 189. The $ENGINE_PAR_STEPMOD_STEP_VALUE should be replaced by $ENGINE_PAR_STEPSEQ_STEP_VALUE instead.
Otherwise you'll get this message in the KSP log:
Variable "ENGINE_PAR_STEPMOD_STEP_VALUE" was not declared!
