Make new bones & Attach the bones to any part of the body bones like picture above,
in my case, i want the bones to move along with the hips, so i attached it to cf_J_Kosi02_s.

After that,

Weight Painting, This is the part where Experience & Skills play a Huge Role,
I do Audio Mixing in the past, this works pretty similar,
I will not get in too much depth here, because it requires too much of a lecture to master this specific skill with solid fundamentals.

After you’re done with weight painting, your mesh is ready to export to .fbx , and then you can drag & drop the .fbx to your SB3Utility,
in my case, i use automated scripts, so it will save me alot of time & repetitive mouse movements, especially with big screen, trust me, you’ll need it soon, or you risk getting carpal tunnel syndrome after 50th iteration, lol.

Above is the assetbundle of my mod, i use automated scripts to generate it.
As you can see, everything is already in prepared and all i have to do is replace them,

First, i replaced the cf_J_Root with my new cf_J_Root that have extra bones, then, i can drag the mesh to replace the SkinnedMeshRenderer,
Repeat this step everytime i make changes to the bone position,

Above is the preview of my mesh, i will make sure the bone is there, and then i can continue to next step

Next, i Double click on Dynamic Bones MonoBehaviour, and i drag & drop the root of the bones that will be affected by physics there, i also adjust those Damping, Elasticity, etc stuff later to tweak the law of physics to my liking.

Then, i click additional_bones, typing in the Animator name on first column, and my root bone names on the next column,
that is important, so the plugin will recognize your new bones and add them in when you load your outfit in game.

That’s it for now, the shorts is available on My Patreon