Create search functionality in the fields section of the RadPivotFieldList. 

Add filtering support for the aggregate descriptions (PropertyAggregateDescription).

Currently, there is such feature for the row and column group descriptions.
https://docs.telerik.com/devtools/wpf/controls/radpivotgrid/features/localdatasourceprovider/filtering

Setting the Expanded property of the GroupsExpandBehavior assigned to the RowGroupsExpandBehavior property of RadPivotGrid to True, and the RowSubTotalsPosition to None, leads to an error. 

To work this around set the RowSubTotalsPosition to Top. 

Or set the IsExpanded property of the corresponding PivotGroupHeader controls manually.

public MainWindow()
{
InitializeComponent();

// the Opacity is used to avoid the flicker that appears because the groups are rendered just before the collapse logic kicks-in.
this.pivotGrid.Opacity = 0;
this.pivotGrid.Loaded += PivotGrid_Loaded;            
}

private void PivotGrid_Loaded(object sender, RoutedEventArgs e)
{
Dispatcher.BeginInvoke(new Action(() => { 
var headers = this.pivotGrid.ChildrenOfType<PivotGroupHeader>();
foreach (var header in headers)
{
header.IsExpanded = false;
}
this.pivotGrid.Opacity = 1;
}), (DispatcherPriority)3);
}

Add support for Hours/Minutes/Seconds steps. Also, add a DayNumber option.

With the current implementation the top level header only visually appears as one cell, however it stretches the subheader column below (check PivotGrid(Now).png).


Looking the attach file,now the XAML is following:
<pivot:LocalDataSourceProvider.AggregateDescriptions>
                        <pivot:PropertyAggregateDescription PropertyName="AccValue" CustomName="total"/>
                        <pivot:PropertyAggregateDescription PropertyName="IncValue" CustomName="increased"/>
                 </pivot:LocalDataSourceProvider.AggregateDescriptions>

 <pivot:LocalDataSourceProvider.ColumnGroupDescriptions>
                        <pivot:PropertyGroupDescription PropertyName="SystemDeviceCode"/>
                    </pivot:LocalDataSourceProvider.ColumnGroupDescriptions>
the SystemDeviceCode column just use one column ,like the attach "PivotGrid(Now).png",when the text is long ,the first column "Total" is too wide .
I hope like the attach "PivotGrid(desired).PNG",the SystemDeviceCode column can span two columns.
     and the data struct:

 public class DayStruct1
    {
        public string HourNum { get; set; }
        public string SystemDeviceCode { get; set; }
        public double AccValue { get; set; }
        public double IncValue { get; set; }
        public DateTime Date { get; set; }
    }//

Currently when a header value is empty the displayed text is "(blank)" regardless of the application's culture. Localize this value or allow the developer to set this value more easily.

If you want to manually localize the "(blank)" text you can define a RowHeaderTemplate and ColumnHeaderTemplate (or template selector) and replace the default text with its translation. You can do that via IValueConverter.
(http://docs.telerik.com/devtools/wpf/controls/radpivotgrid/styles-and-templates/templating-cells#using-custom-cell-and-header-templates)

I want to create CustomDistinct aggregate, I did it successfully for LocalDataSourceProvider, and I need it also for QueryableDataProvider.

See: http://www.telerik.com/forums/custom-aggregate-for-queryabledataprovider