To hide a module select Hide from the context menu of the module. The module will vanish from the content.
To reveal any hidden content, click the Show hidden content text at the top of the Organise content section.
The module will display grayed out with (Hidden) appended to the name as below. Note that the cogwheel has been replaced with a archive box.
Click the archive box to the right to bring up the context menu and select Unhide