To modify the visibility of a disk:
Select the disk in the local menu; then click the Show button to make it visible or the Hide button to make it invisible.
You can use the Visibility pane of the Files toolbar item to act on the visibility state of a disk, folder, or file.
If System Integrity Protection is turned on, you can't modify the visibility status in /System, /bin, /sbin, or /usr (except /usr/local); or any of the built-in apps and utilities.
Select the disk in the local menu; then click the Show button to make it visible or the Hide button to make it invisible.
Click the Show Folder button to make it visible or Hide Folder to make it invisible; then in the dialog that appears, select the folder.
These two buttons can possibly influence the visibility of a disk.
Click the Show File button to make it visible or Hide File to make it invisible; then in the dialog that appears, select the file.
Click the Show Application button to make it visible or Hide Application to make it invisible; then in the dialog that appears, select the application.
Warning: All of these operations reopen the Finder. Verify that no operation is in progress (such as copying, moving, burning, and emptying the Trash).