'Generate Server Template' is only enabled when the Studio is installed in enterprise mode (choose all components). That means install weblogic in a Oracle Home, then choose install ODI in the same Oracle home in enterprise mode, the button is automatically disabled when ODI judge some required modules are not installed. so If you use Studio in Companion CD(by unzip) or not choose all components when install ODI, the button is disabled
Another notice, if you want to create a weblogic domain with a JEE agent and odiconsole deployed, you don't need this 'Generate Server Template', you just need install weblogic then odi, declare the physical agent/logical agent, then create domain(choose jee agent and odiconsole), go on as the doc said. This button is used optionally, not required, if you want to deploy another Jee agent, you can choose to use it.