Is it possible to apply the sell price onto the compare at price on my products?

Your products use a normal price and you'd like to apply this value to the field 'compare at price'?

Simple with the Sc App!

First select the concerned producs - using the CTRL key of your keyboard, or the mass selection iconif you want to take into account all products in the list.

Then right click on the products to display the popup menu, and select Mass update > Copy the sell price to compare at price - Products

And that's done!