I guess you've lost me. Can you explain what you're doing, step-by-step, what is happening, what you expect to happen, etc. so I can understand why you think it's not saving?
1. Launch Shinki.Net launcher, select Diorama STudio, log in.
2. Select first option, the model editor.
3. Selected Valona.
4. Select first option, the stock poses, chose a pose from list.
5. Stuck equipment on figure.
6. Clicked "SAVE" button, typed 'TestPose' in empty text box at bottom of dialog.
7. Clicked "SAVE" button.
8. Clicked quit.
9. Repeat steps 1 & 2.
10. Select second option, which are poses I have created.
11. Saw 'TestPose' in list.
If you're getting error messages or anything, a screenshot of the message could be helpful.
Something like that might clear up whether you're doing something different or or missing a step or something, but it's very difficult to troubleshoot things remotely like this without very detailed information.