After following an official tutorial (https://www.youtube.com/watch?v=o2pda-px7N4&t=220s), I've come to realize that reproducing the exact same steps as seen in the linked video just refuses to provide the same results. In the Morph Slider Editor, clicking OK (even with 'auto apply to current character' checked) will give me a progress bar, and then nothing else afterwards. The window remains open, and no custom morph sliders corresponding to my sculpt can be seen anywhere in the morph editor.

I've attached screenshots of both the CC4 window, and a preview of what the sculpt should look like as I've edited it in Blender. Note that no new vertices have been added nor removed; I sculpted with dynamic topology off on a new blend shape set to 1 (as instructed by your tutorials). All sculpting was done on the original geometry.