It's unenforceable. Check page 19 of "Programming the Logic Theory Machine", by Newell and Shaw, published in 1957, for prior art.
That's why the legal system is wrong.
1. The linked list was described in 1957 or earlier.
2. The cited mention of the linked list also considers more complex permutations of lists.
3. This patent effectively describes adding a single set of items to multiple lists (I haven't read the patent, so I may be glossing over details).
4. #2 demonstrates that such a permutation of the concept of a list would be obvious to anyone skilled in the art.
5. Therefore, the patent is invalid.