How to manipulate itksnap workspace file(.itksnap) via itksnap command line tool (itksnap-wt)?

Beginner Questions
1

Hi!
I want to manipulate itksnap workspace file(.itksnap) via itksnap command line tool (itksnap-wt).
The first step is try to add another .nrrd image in to a workspace file. I trid this command:

itksnap-wt -i 1only.itksnap -layers-add-anat 2.nrrd

It give me this result

INFO: picked layer Layers.Layer[001]

But it still only has one layer:

itksnap-wt -i 1only.itksnap -layers-list
2> Layer  Role  Nickname  Filename                                  Tags  
2> 000    Main            /home/ziqi/Desktop/ITK_PROJ/build/1.nrrd

Did I do something wrong?

2

This question is better posted to ITK-SNAP users mailing list.