Edit: Already Solved. Thank you.
Although I understand some modding features are not available yet, but I needed some more sample assets in modkit files.
I managed to make custom hair, accessories, outfit parts, freckles, makeup, body because there are sample files including their materials, textures and meshes. But 1 thing missing is “HEAD/FACE” assets.
I tried to make full skin texture mod (body+head), but I couldn’t complete it because in AvatarParts folder, there’s only body and groom. But no head/face assets found. It will be great if those are included too. Thank you!