The documentation on plugin:CreateToolbar() is still incorrect months after its behavior has been changed.
It originally allowed plugins with the same toolbar name to combine, but that is now no longer the case. As seen from this post: Plugins with the same toolbar name don't combine, this was an intentional change:
However, on the page documenting it, still claims that it can get the toolbar of the same name.
https://developer.roblox.com/en-us/api-reference/function/Plugin/CreateToolbar