1. download the "Addition.blend" file.  located the addon folder. normally it is at C:\Users\Learn\AppData\Roaming\Blender Foundation\Blender\3.5\scripts\addons\RandomHeadGen  if you have set up custom folder path, open that folder instead

2. there you will find "RHG_HeadMeshFile.blend" and copy the "Addition.blend" file here

3. open the "RHG_HeadMeshFile.blend" in blender, in the addon tab you will find "Append Additional Shapekey" at the very bottom, click it, save the blend file and close it, it is done.

4. next time when you import a head, all the new shapekeys are included.

the default addon folder is "C:\Users\UserName\AppData\Roaming\Blender Foundation\Blender\3.3\scripts\addons\RandomHeadGen", often it is not convenient for user to locate. now you can specify a folder and possibly set up one head mesh per project. here is how:

1. go to the default addon folder mentioned above. copy "RHG_HeadMeshFile.blend" and "RHG_ARkit_Mesh.blend".

2. choose a convenient location and create a new folder, for example "Custom Head for Project 1" in D drive, go to the folder and paste "RHG_HeadMeshFile.blend" and "RHG_ARkit_Mesh.blend" there.

3. go to blender Random Head Generator addon preference and point to the folder, please note do not point to any blend file inside, do not add any empty space and save preference. it should be like this:

4. you can set up multiple folders repeating above steps. using blender bookmark you can quickly switch different projects. modify "RHG_HeadMeshFile.blend" inside each folder, such as mute certain shapekeys. if the custom path is empty, it will use the default addon folder.