控制z - index Fabric.js

In fabricjs, I want to create a scene in which the object under the mouse rises to the top of the scene in z-index, then once the mouse leaves that object, it goes back to the z-index where it came from. One cannot set object.zindex (which would be nice). Instead, I'm using a placeholder object which is put into the object list at the old position, and then the old object is put back in the position where it was in the list using canvas.insertAt. However this is not working.In fabricjs, I want to create a scene in which