Hi Alain!
For sforzato make a "Custom text" entry in the Human Playback Preferences as described above. The keyword could be "sf" or "sfz".
The normal dynamic expression for sf or sfz will not work for HP. So you have to create your own as Technique Text. Open the Expression tool, go to Technique text and create a new one. The text should be the same as your keyword (probably sf or sfz). In order to look like a normal sforzato marking in your score, change the font to Maestro (size 24, not bold) and let it appear below the staff. For the next note make an expression like "ord." to switch back the articulation (unless you want several sforzati in a row).
Andi
Vienna Symphonic Library