Clicking 'Die' then gives you the options for the active sim to cause the assassin to 'Die By Poison' or the corresponding death for the assassin level of the assassin. I'm not sure when this appeared but I see now that when I play another sim as active (same household, or otherwise and not necessarily with or without the assassination skill) and click on my assassin, the first interaction bubble option that appears along with 'Friendly', 'Romantic', etc. It is generally working great (much much better than the early days of this mod) and adds some nice drama to my game. I always play with one or more sims in my town that have the assassination skill.
