How to use the hammer and sickle in the tower to kill someone?

The only chance that I even get someone in that room is to show the Constant the blue print as the designer. Then the Constant would go to the tower and call Sophia and ask her to go upstairs. But after their private conversation, the Constant stood by the table for a while without any interaction option activated, and Sophia just walked away which left me no chance to do it either. I knocked her out and dragged her near it and still no interaction option appeared.

According to what I learnt from “Another Life”, I should lure someone to get in front of it and launch the kill from behind. But whom, and how?

hmm… guess what. I used the coin-magic and made it.
Coin-magic, nice trick of position control.

Yes, coins have hidden strong power in the game.
As far as I remember you need to kill anyone with that thing, not necessarily a target.
There are two guards in that room. You can occupy one by a weapon or overflowed sink and then lure the second to that thing and do the job.
But if you’re up to the target for this one, just get rid of those two guards, target’s guard and lure her there. Then pisition her right with a coin and you’re done.
You can use weapon lure trick on a target, it will be easier to take her there.
Or, well, create a contract with one of (or both) the guards there as a target