I'm not sure what JMP version you are using (JMP19.3 hasn't been released) but you might have to modify your Preferences to make changes to GraphBuilderGroupBoxes. Also, if you can get the vector graphics, couldn't you just remove the title and add your own title?
Example using Powerpoint

Not really what you most likely want is to increase the size

So delete it and just add your own title as text box

-Jarmo