Hi Hao
It looks like you were just at the right place... but didn't read the output ?
Notice in your output of "devices device xxxx ned-settings ?" is says "cisco-ios cisco-ios ned-settings"...
But you didn't seem to go there...
So i did for you 
admin@ncs% set devices device ios0 ?
Possible completions:
ned-settings - Control which device capabilities NCS uses
netconf-notifications - NETCONF notifications from the device
admin@ncs% set devices device ios0 ned-settings ?
Description: Control which device capabilities NCS uses
Possible completions:
cisco-ios - cisco-ios ned-settings
use-confirmed-commit - Control usage of confirmed commit
(skip...)
admin@ncs% set devices device ios0 ned-settings cisco-ios ?
Description: cisco-ios ned-settings
Possible completions:
api - Configure API (new API features/changes)
(skip...)
read - Settings used when reading from device
write - Settings used when writing to device
admin@ncs% set devices device ios0 ned-settings cisco-ios write ?
Description: Settings used when writing to device
Possible completions:
config-output-max-retries - Max number of retries (one per second) when sending config command to device
config-warning - Device warning regexp entry list
device-output-delay - Delay in milliseconds after each config command output to the device
inject-answer - Inject answer to question from device received when applying config (commit phase)
inject-command - Inject command (before or after) specified config-line upon commit
memory-method - Change method to write config to memory
memory-setting - Configure how and when an applied config is saved to persistent memory on the device
number-of-lines-to-send-in-chunk - Number of commands lines in a chunk sent by the NED to the device.
replace-commit - Replace (or filter) config when writing to device
admin@ncs%
All good! (but with a slightly different format)
One other comment - it also helps to "look inside the NED" if you have questions. For example, in searching the YANG modules, you can see that the "ned-settings" are in the yang file "tailf-ned-cisco-ios-meta.yang" ...
However, as you've discovered. the structure of this yang module appears to have changed from 5.x to 6.x
the new structure (obviously) matches what you're seeing at NSO CLI...
hope that helps..
Gregg
