The application was created to help creating custom NPCs using the RaceMenu + CharGen Extension mods from Expired. It will only automate the task of transferring the blocks from one .NIF file to another.

It requires some knowledge about how .NIF files work, and all this tool does can also be done with NifSkope, so I encourage you to use that tool if you need further customizations and also to check if the resulting files work correctly.

Requirements:
NET Framework 4.0 (and 2.0)
Visual C++ 2012 Redistributable Libraries (32 bit)

Not required but this application doesn't make sense to use without:
RaceMenu by Expired6978
CharGen Extension by Expired6978

Notes:
Some elements (hairs usually) may not be able to be merged because they have bones assigned that are not found in the target element. The application will notify those cases and will not allow to perform a merge of those elements to avoid causing CTDs.

Headparts.csv:
This file is a list of elements (hairs, eyes, heads, etc) that is used to know which type of element is each block found in the .NIF file. Since each computer has different mods installed this list will not be complete. I provided a script for TES5Edit that can be run to create this list automatically.
Without this list (or if it's incomplete) you have to manually assign which block is to be merged to the other blocks.
The list provided already contains the vanilla head parts and some other mods.

Disclaimer:
Use this application at your own risk, if instructed it will overwrite files so backup files manually before using this tool.