Is there a way to adjust timings and/or transitional effects on a "per slide" basis?

WOWSlider allows you to adjust the timings and transitional effects for the slideshow as a whole, but not on a ‘per slide’ basis.

To edit the timings for your slideshow as a whole, open the properties window by going to Slider -> Properties in the menu bar. Go to the ‘Design’ tab by clicking on the button at the top of the window. You will see you can change the ‘Transition effect’, change the delay between slides and change the effect duration in this window.

You can mimic a unique transition effect for each slide by selecting multiple transition effects for the slideshow, which will then be applied at random.