This function appends the directory dir to the set framesetpath option if not already present. If prepend is 1, prepends dir to the framesetpath path, removing any later occurrence of the directory.

If there is an Arbortext-path\custom\framesets subdirectory at startup, the \custom\framesets path is automatically prepended to the frameset path. Putting your entity files in the \custom\framesets subdirectory makes them automatically available, avoiding manual steps to add them to the path.