About Waveform and Thumbnail Cache Files
Waveform and thumbnail cache files are temporary files Final Cut Pro creates when
you import media files. Neither type of file requires much hard disk space, so you can
choose to store them on your internal disk or an external scratch disk. If these files are
moved or deleted, Final Cut Pro can re-create them when you open a project file.
To set locations for the waveform and thumbnail cache files:
In the Scratch Disks tab, click Set next to the appropriate item.
In the dialog that appears, locate and select the disk you want to use.
The specified disk is listed next to the Set button, along with the amount of available