Visual saliency for image design

Just to make sure: Are you talking about changing saliency or determining saliency? 

If you want one part of your image to stand out, one thing you can do is duplicate the layer and add a layer mask to the subject. On the underneath layer, you could blur it or drop the opacity or add effects, etc., so the masked subject on the upper layer is more prominent.

I see that you've asked the same question in Illustrator and Premiere:

https://community.adobe.com/t5/premiere-pro/video-saliency-tool/m-p/11971826

https://community.adobe.com/t5/illustrator/visual-saliency/m-p/11971837

~ Jane