How to make slider marker move automatically?

I’m trying to provide an example of how a sequence of images should be rated by having the slider marker move automatically according to the correct ratings.

In the PsychoPy version I just added:

slider.markerPos = rating[currentImage]

which worked well.

But on the online version I get this error:

  • TypeError: Cannot set properties of undefined (setting ‘markerPos’)

From what I understand, markerPos is undefined until there’s a click on the slider. Is there any other solution for making the slider marker move without the participant interacting with the slider at all?