https://sims4studio.com/thread/305/create-item-new-joint-assignment?page=1

This tutorial will show you how to change a joint assignment so that an accessory will move appropriately with the new position your mesh has.

What you will need:

Sims 4 Studio (stable version or 2.0.0.6 and above)

Clone your item:

1. Select the item you wish to clone and hit Next. For this tutorial I've chosen a ring. When the model viewer screen comes up switch to the Mesh tab and export LOD 0.

• LOD 0 is the main mesh that the player will see when zoomed in close to the Sim wearing the item. LOD 1 is seen from a short distance away and the other 2 are seen from far away.*

Change the Item's Joint Assignment in Blender:

2. Click on your .blend to open it in Blender and move the mesh where you want it to be. I've moved the ring from the middle finger to the ring finger.

4. Click the n key on your keyboard to bring up the side bar menu. Scroll down in that menu until you see the Show Weights line and put a check in the box there. Your item will change color.

5. Over on the right you will see the Vertex Groups box with your joint list. Click the plus sign there.

6. Enter the new joint name on the list if it isn't already there. If you need the name of the joint to enter go to this list to get it: Joint List for Sims 4 Skeletons

8. Now, with your item still selected, click the joint your item was assigned to. When you pick it the item will still be red.