Just a clarification to the comments here:
Per the file format spec, either is allowed (i.e. any valid, relative path for your OS).
Per the LDraw Library standard (i.e. Official Library parts), only backslash is allowed
Per the file format spec, either is allowed (i.e. any valid, relative path for your OS).
Per the LDraw Library standard (i.e. Official Library parts), only backslash is allowed