As of version v2.1.1 the easiest way to grant all your macros permanent access to files and folders is the built-in macro:

Macro > Application > Manage Macro File Access

If you use this macro to grant access, access will be restored automatically by Nisus Writer for any and all subsequent macro execution, without the need for any macro code to explicitly use the commands below. This built-in macro also can list and rescind previously granted access.