Half-sibling portrayal in RM8 software

I have a half-sister (shared mother), how do I portray this in the software? It only seems allow me to add her as my sister linking to my father! I’ve seen a couple of comments about adopted children and difficulties with the GEDCOM file structure representing these relationships. Is this similar or am I missing something?

Highlight your Mother
Right click her and Add child. Add or choose your step-sister.
Decline adding under your father during same dialogs.
Add actual father. Right-click step-sister and Unlink from your father


Thank you, that worked, some of the autolinkings work against you!