Recently, we confuse when New Task layout for Action is different with the one we define in the Salesforce setup menu - Setup | Create | Global Actions | Actions, click Layout link in New Task.
Here is our New Task layout for Action:
If we check from Chatter Feed action, the layout is correct:
Then we continue to verify in one/one.app simulator, and it is also correct there :
But, when test from Salesforce1 app in mobile device (iOS or Android), the layout order is different. Although all the fields defined is still there, but Subject will always at top, continue with Details and etc, even Subject is not defined at top in the action layout. Here how it looks:
Caused and Solution
Finally, we found it caused by a checkbox in Setup | Customize | Activities | Activity Settings, there is an option of Show simpler New Task form in Salesforce1. If this option is enabled, you will see New Task in Salesforce1 app in mobile devices as above.
You can simply deactivate it and the layout will be back as defined in the action layout.
Reference: Creating Tasks using the Salesforce1 app