Hello,
No, unfortunately it’s not possible by default. But if you want to be able to set which products will be displayed in slider you can add Up-Sell products instead of Related Products slider.
To disable Related Products go to Theme Options > Single product Page > Show related products > OFF.
Watch video tutorial how to add Up-Sells https://www.youtube.com/watch?v=GF8vdvjmrIw
After that go to Theme Options > Single Product Page > Location of upsell products > After Content.
Regards