Create additional scratch disc location
HI
I am getting the scratch disk is full error on PS.
I would like to add an external drive as my default hard disk location but cant seem to either deselect the current default drive OR create a new location?
I am running Photoshop version 21.02 on a MacOS High Sierra version 10.13.6
I have tried holding down the command-option button when opening but that does not help ( just changes the Cancel key below to a Reset key which does nothing if i select it?)
HELP
Thanks

