as I've pointed out before, Courage's theme for the Romulan Commander in TEI is pretty much a variation on Steiner's Romulan theme. Structurally they're almost identical -- a held note, then three descending pairs with a bit of a pause after the second one and the third pair ending on the same note as the first, then the same three pairs repeating, etc.
Yeah, you've said that before (I think when we were having a discussion about whether Duning was the only TOS composer to borrow from the other composers). I'm not sure I buy it.
The theme for Spock's scenes with the Commander is heard mainly in "Vulcanization" and "Back From Dead / Commandeered" (s3d3 tracks 6 & 10). They don't sound anything like Steiner's "Marlena" cues (s2d3 22-24-25), certainly not rhythmically and they may not even be the same key. (I can't tell about the intervals. My ear for intervals is, to put it kindly, "untrained").
What the theme most sounds like to me is Courage's eerie season 1 music. I have not listened to the Courage season 1 music since the set came out, but I think the Enterprise Incident "Commander" cues would not sound out of place in the Cage score, or Man Trap. Much more in common with those than with Steiner's Marlena cues – at least, that's what it sounds like to me.