It appears the standalone player will only play from beginning to end. With the only possibility to skip ahead being to manually click forward slide by slide. On a 90 minute video, that is difficult.
The reason I ask is, sometimes I get lag on the standalone player, or a freeze. In that case, I would like to be able to start the standalone player for example from the halfway point of a 90 minute presentation, instead of having to start from the beginning all over again.
Currently it is not possible to start the slideshow at a certain point. However you can add Chapter Markers in your slideshow (control click on the first slide of a chapter and select “Add Chapter”) and jump to them with the left/right cursor keys while holding down the alt key.