Field Read/Write Permissions
By default, you cannot modify auto-filled system fields on a step, while all custom fields created and such system fields as Title, Description and Due Date stay editable.
If necessary, you can protect the editable fields from being modified by changing read/write permissions. This may come in handy if the fields contain essential data you don't mean to lose.
To change read/write permissions:
1. Open the Step properties window. Click Field permissions.
2. Switch between Editable and Read only to make fields editable or display-only. If the Editable column is grayed out (it is for almost all system fields), this means the field is auto-filled.
3. When finished, click the Save & Close button.
4. Click Save Workflow.
Changing read/write permissions for fields on a step doesn't affect similar fields on the other steps. You have to change permissions for them individually.