Yes, change the url, click Done and then re-deploy. That last bit is important since it is the re-deploy that actually changes the name.
just remember that after re-deploy, the underlying instance folder will also be renamed. So if you are using an IDE like VS Code to edit front-end code, you will need to change to the new path. The node itself is fine with renaming.
I renamed the url as instructed but the index problem was still there.
I then updated uibuilder to the latest release V7.3.0 and changed my browser to firefox and now it ALL works!
Thank you for your time