https://github.com/kwsch/PKHeX/blob/f6fb54aeccb4aa58614dfc684bc7818a22eb6e16/PKHeX.Core/Editing/Bulk/BatchEditing.cs#L36
https://github.com/kwsch/PKHeX/blob/f6fb54aeccb4aa58614dfc684bc7818a22eb6e16/PKHeX.Core/Editing/Bulk/BatchEditing.cs#L470
.OT_Trash=$[]BE,EF,CA,FE,...
keep in mind the property setter will accept it ONLY if it matches the expected length (gen6+ = 24 for both OT/Nick). Just check the length expected in the pk*.cs class