moving objects on screen using JS?

It's true you can't change the top and left values. But you can change the margin and probably padding.

I made a long bar with a dot at the end as a progress indicator, 2000px wide and set left to -1988px (since at least part of it has to be in frame).

I then changed the left margin according to proportion of the way through the slides using a javascript advanced action (prefix your object with "re-" and suffix it with "c":

const elem = $('#re-Progress_dotc');

var currslide = window.cpAPIInterface.getVariableValue('cpInfoCurrentSlide');

var numslides = window.cpAPIInterface.getVariableValue('cpInfoSlideCount');

var margin = (currslide / numslides) * 100;

elem[0].style.setProperty('margin-left', margin + '%', 'important');

Which gives me this, my image being the orange bar with the dot at the end:

Unless you are working on a responsive project in CP8, you can use motion path for that.

Sreekanth