You can select the Insulation on the diagram - Right Mouse Button menu and select Delete.
Or select the Insulation Run or Insulation Layer in the browser list, bottom left corner.
You have not mentioned whether you are using Capital HarnessXC or VeSys Harness, but if the above does not work for you then please raise and SR and provide more details and perhaps a small sample.
I am using VeSys Harness.
Both methods you mentioned worked for me.
I was not aware the insulation also showed up in the browser list, so that is good to know too.
I thought I had tried directly selecting the insulation before, but must have always been selecting the bundle. Before, I had been mainly trying to delete the insulation by using the "Edit Insulation Run" dialog box.
Thanks for the help Pat!