When i set the slideshow media input to manual, where/how i can step to the next picture?
Manual mode means that you will select the image index manually.
So changing the index value will change the image.
If you want to select the next image, you have to create an interaction on the "index" property then set the interaction to "accumulator". That way triggering the interaction will had +1 to the index thus displaying the next image.
More on the interactions
Thank you! Works perfect!