Aaron -
Looking at your sequence file it appears that you are developing in TestStand 2.0.1. Not that this helps you now, but in TestStand 3.0, NI added a full set of classes for the Adapters, editing code modules and parameters. This in general is an easier and more strictly defined way to develop steps programatically.
Now for TestStand 2.0.1. Looking at your code and the bitmaps you are not creating the right container, of type SequenceArgument. I am not sure if internally the SequenceArgument data type might map to an internal class that has additional information that a generic container does not have.
You should be able to call
spProperty->NewSubProperty( "TS.SData.ActualArgs.arg0", TS::PropValType_NamedType, FALSE, "SequenceArgument", Option
_InsertIfMissing);
This will add the arg0 element before you calls to update its subproperties.
Let me know if that makes any difference.
Scott Richardson (NI)
Scott Richardson
https://testeract.com