Hi,
The format used while adding advanced value is <parameter><value>, for this scenerio you would have to click on add row and then for parameter name use workingDir and for value use /vmfs/volumes/46f1225f-552b0069-e03b-00145e808070/vm-snapshots. However I have always used CLI to edit the VMX files, if you want to follow the KB as it and have access to ESXi Shell using SSH then it would be easier to cd to the virtual machine directory and then use the vi command to edit the VM.VMX file.
-Arun
http://highoncloud.blogspot.in/
About VMware Virtualization on NetApp