Hi friends, I couldn't find answers to my questions. So I decided that this topic will be used as a diary, in which other participants can help me to move towards my goal.
And so what I know: The Elder Scrolls V Skyrim Anniversary Edition - this is the same The Elder Scrolls V Skyrim Special Edition only with some mods approved by Bethesda Softworks.
I know that without special 3D modeling skills you can use Blender and FaceBuilder add-on.
I also know that RaceMenu and Expressive Facegen Morphs SE mods allow you to expand the possibilities of customization in Skyrim. However, RaceMenu and Expressive Facegen Morphs SE are no longer supported by the authors and have an old version. I think this is a bad thing.
I also know that Skyrim characters' heads have their own "Mesh", which RaceMenu and Expressive Facegen Morphs SE extend with new features. And the FaceBuilder add-on has its own "Mesh", which prevents it from being loaded into Skyrim.
It seems like there are two options to check out:
1. Export the mesh to Facebuilder and create a face from the photo with the original Skyrim stack.
2. Learn how to convert the mesh in Facebuilder with the created face to a matching Skyrim mesh.
Also, if I understand correctly, the eyes and hair are added in a separate program.