found a issue with Hub variables @gopher.ny or @bravenel if you just have a device and create a connector and not use the variable in a rule it wont pick up that its being used but that stops the link working and so you can't rename the variable.
Yeah, a connector in use is not the same as a variable in use. You can rename the connector on its device page. The rule itself has no way to know that it's a connector, so it can't mark the variable in use.
This isn't going to change. Renaming a variable is only available for one in use. In all other circumstances (aside from using a connector only), an unused variable can just be removed and a new one created with a different name. Like said, using only a connector and then wanting to rename the variable is an edge case, one that is not compelling to change the Hub Variable UI for.