There are multiple ways for a VRChat avatar to "spawn" or "place" an object into a VRChat world and have it stay there while you move around, etc.
**1. Use a particle system**
Add a "Particle System" component to a GameObject. Configure the component like the screenshot:
- "Simulation Space" to "World"
- "Start Speed" to "0.0001"
- Renderer - "Render Alignment" to "Velocity"
Then select a mesh as the Renderer (note you are limited to meshes with only 1 material slot).
This will make Unity render your particle once and have it stay there forever (or until you turn off the particle system with an animation).
Preview:
https://cdn.vrcmods.com/uploads/user/1/custom_imgs/ad49b756876c46c3b4cc92b88341be67.png **2. Use a "Configurable Joint"**
- Add a "Configurable Joint" component to the GameObject you want to "spawn".
- Set the X/Y/Z Motion and Angular X/Y/Z Motion to "Locked". This will tell Unity to have it lock in place while you move around.
You will probably want to hide the GameObject using an animation!
Preview:
https://cdn.vrcmods.com/uploads/user/1/custom_imgs/c3d0c93aa3fe4b8c9c6876ad78c7cd87.png **3. Done**
Toggle the GameObject for it to appear.