You can edit both the pre-defined and the custom widgets. The only exception being the URL value of the pre-defined widgets, which cannot be edited. To edit a widget: Rollover your mouse on a widget to highlight the edit option. Click Edit. In the ...
You can customize the order in which the sections and the widget are to be displayed in the Customer Portal Home Page. Just drag and drop the sections/widgets according to your needs. Click Preview to see the change and click Save.
As of now, you're not allowed to change the color or the theme of the Customer Support Portal. However we are currently working on this feature which would enable you to change the CSS of the Customer Portal page.
No, it is not possible to restrict a particular Departments for selected Customer Portal users. Once a Department is made "Public", all Customer Portal users can access that particular Department.
No, currently it is not possible for a Portal User to view Requests related to other customers. However, a portal user can add requests and track his/her request status in customer portal. For more refer Portal User Action