There is an option to hide them in both v3.1 and v3.2.
Are you open to learn how to show or hide fields?
Where can I find a user guide or manual?
We have no user guides or manuals, sorry. Instead, we can offer you an application which is so easy to use that needs no manuals, provided that you don’t need guidance in project scheduling per se. If you still need to see how to do the basic actions, consider watching one of the awesome video tutorials contributed by volunteers.
Some of the tricky bits and rough corners are documented at http://docs.ganttproject.biz