In your special case maybe a "set of" would be the desired construct. A set of values matches a list of same values in any order.
Nevertheless there is a processed change request for the TTCN-3 language at (CR6088), extending the BNF to support also dynamic lists as parameters for superset, subset, permutation and complement.
The CR was accepted and will be published in the new TTCN-3 Edition 4.5.1 (for details please Section B.1.3.3). The 4.5.1 TTCN-3 Core Language Standard should be available at http://www.ttcn-3.org/.
Please find below the example (from the standard document) that shows the usage as defined by Edition 4.5.1:
type record of integer RoI;
template RoI t_RoI1 := {1, 2, *};
template RoI t_RoI2 := {permutation(0, all from t_RoI1), 4, 5};
// results in {permutation(0, 1, 2, *), 4, 5}
Best regards,
Bogdan