The 64 bit version of 4D on macOS is using POSIX APIs on Mac OS X (like all modern applications) and therefore does not support the presence of a slash character ("/") in a file name or path name.

Using the slash character in a file name or path name or file name is usually something you would want to avoid anyways, as this character is also used as a path seperator on most operating systems, which is why the slash "/" is a forbidden character when naming a file or folder.