When this is set the debugger will try to find kernel modules files that match the ones found by the Linux tracker under this path (including sub-directories).
The path does not have to be an existing host path, it can be any path or pattern for which a path map can then be applied on in the debugger, in order to map this to the actual host directory.
If this is set to an empty string then kernel modules will not be scanned for and the debugger will then only be able to debug kernel modules for which individual path maps have been added.