How do I save a Simulink Test harness by command line/script?

I'm trying to use a script to open and modify a few dozen test harnesses for my model. Excerpt:

sltest.harness.open(modelName, harnesses(n).name);
sltest.testsequence.addSymbol(blockName, signalName, ...
        'Data', 'Output');

However, I can't find a command for saving the changes. If I use

    sltest.harness.close(modelName, harnesses(n).name);

I get the following error:

Error using editHarnesses (line 32)
Unable to close the test harness 'xxx' since it has unsaved changes.  Please save the harness and
try the close operation again.

The model stores its harnesses in external .slx files.

Answer 1

[Simon Ahrens]

Nevermind, I'm silly and expected a dedicated Simulink Test save function. In fact the Simulink function

save_system

works just fine.