Onion skinning / ghosting in Blender ?

I recall Blender has ghosting. However I don’t recall if I can set it to remain on certain frames only (to keep certain poses visible).

So I saw this video:

and now I am wondering how can I, using any of the existing tools/add-on in Blender, set ghosting to be present on certain frames of animation and remain there ? Is it possible ?

For armatures you have the Ghost settings in the armature properties

Correct. But as I mentioned, I am not quite sure if that functionality we have in Blender can ghost only particular frames.