Here, you will see folders with long hex codes. You need to replace the container with the save file inside. You may need to use the (available on GitHub) for Game Pass saves.
Normally, special "Seeds" (specific level layouts with unique features like massive half-pipes, endless downhill slopes, or trick-friendly parks) are rare rewards or must be discovered. In a 100% save, you have access to the entire library of seeds. descenders 100 save