I believe question is about plugin-ext, you can create extension outside of Developer Studio using create.bat file under folder structure liferay-plugins-sdk\ext\.
Navigate to ext folder of your plugin-sdk, then you have to run window's command in command prompt like create.bat extension_name "extension_display_name".
You can build/deploy this created ext using ant commands. You can find several ant targets in build-common-ext.xml.
Hope this would be helpful, if your question was related to something let us know.
