It is possible to edit the macro, in order to change some metadata: size, toolbar & border. However I don't get the option to change the name.
If I go into the page code and change the macro's diagramName there, the macro's connection to the diagram data seems to break.
You'd need to copy, then change the names of the corresponding attachments copies on the page (both the diagram XML and the PNG preview). You should copy and rename them, rather than rename, so that the page history is intact.
In additional, you need to edit the storage format for the page (source editors are available for both Confluence Server and Cloud), find the "diagramName" parameter in the draw.io macro for that diagram and change the value to new name.
Atlassian supply a free source editor for Server, but its operation and updating aren't always great.
There's always pay-for source editor for both Server and Cloud, which I've found to work really well.