I can use the 'Extension Management' option in the free trial and I can import the jar files. Initially, there is no list of extensions. So, I developed a custom wrapper and imported it to test its functionality.
In your case, If you want to use extensions for a distributed file system like S3 wrapper, you have to purchase the full license.
To know more about developing custom wrapper, you can have a look at the section [Developing Custom Wrappers](https://community.denodo.com/docs/html/browse/7.0/vdp/developer/developing_extensions/developing_custom_wrappers/developing_custom_wrappers#developing-custom-wrappers) of the Virtual DataPort Developer Guide.
Hope this helps!