Right click on the asset in Content Manager.
Choose Open...
Choose Edit Config file text...
Your text-editor will open up - usually Notepad on the PC.
Look for the container that has default in it.
A container has a { and a } with text in it. There will be lots of them, so look for this one in particular. Unfortunately, I repaired my installed version ages ago and don't have the exact line to show you. Perhaps someone else can help with that.
Delete that container.
Save the text.
Close Notepad.
Back in Content Manager - right click on the asset and choose Submit to close the asset again.