Animation Retarget Toolkit 4.26 + 4.27

 I found these problems with retargeting animation,
the rig asset in UE is not changeable, you can just use a humanoid structure, to retarget all other kinds of the skeleton structure, 
there is no ghost pose option, you always have to open two skeleton side by side and guess where the other bones should be
assigning of the bones in the rig config should be performed on both source and target skeleton
the retargeting process is too scattered, and confusing (you can find lots of youtube video which are trying to describe the retargeting process)
modify pose is not intuitive
there is this Duplicate and retarget animation window which is not good enough and there is no reason to make it separated(I think),
there might be some others which I can't remember
I tried to solve them one by one
the rig config asset is editable you can make it from the source skeleton
no need to set rig config for source skeleton, the tool is creating the rig config from the source skeleton and set it automatically
with the ghost pose option no need to guess the pose you are seeing it
modify pose is more clear by the toolbar menus
all retarget process is in one single window, no need to go here and there
easy bone mapping by just clicking on bone visuals