The Custom folder only appears in the control block palette after exporting or sharing custom modules. You may need to close and reopen the CAF for the folder and modules to appear.
An exported module is saved in a file in the C:\ProgramData\Johnson Controls\MetasysIII\ CCT\UI\Custom Control Modules directory on your computer using the user specified name of the module with a .caf.module file extension. You can also create sub-directories under the Custom Control Modules folder.
You can share the exported file with other users by placing a copy of the file in the Custom Control Modules directory on a different computer; the module appears in the Custom folder in the palette the next time the tool is started on that computer.
See Importing and Exporting a Module in the Configuring a System section. For information on upgrading modules, rerunning system selection, and other versioning details, see the Upgrading System Files section.