I'd like to use a shadow variable to customize the tabu acceptor.

Let me explain it by using "vehicle routing" example.

The Entity "Customer" has variable "previousStandstill".
We can use tabu by the Entity and the Value but not by a shadow variable "vehicle".

For example,
Customer 1, 2, 3, 4 are in vehicle A.
Customer 5, 6, 7, 8 are in vehicle B.
And there are more customers and vehicles.
Now, let's suppose we swap customer 3(A) with customer 7(B).

The Tabu by "vehicle" property would prevent change and swap moves which relate vehicle A and B in specified tabu size.