MainWindow.xaml

<dx:DXWindow x:Class="MenuCustomization.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
    xmlns:dxdb="http://schemas.devexpress.com/winfx/2008/xaml/demobase"
    xmlns:dxsps="http://schemas.devexpress.com/winfx/2008/xaml/spreadsheet"
    xmlns:dxb="http://schemas.devexpress.com/winfx/2008/xaml/bars"
    xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
    xmlns:dxspscore="clr-namespace:DevExpress.XtraSpreadsheet.Commands;assembly=DevExpress.Spreadsheet.v15.2.Core"
    xmlns:local="clr-namespace:MenuCustomization"
    Height="400"
    Width="800"
    Title="Spreadsheet">

    <dx:DXWindow.Resources>
        <dxsps:SpreadsheetUICommand x:Key="commands" />
    </dx:DXWindow.Resources>

    <!--region #PopupMenuCustomization-->

    <dxb:BarManager x:Name="barManager1" ToolbarGlyphSize="Small">
        <dxb:BarManager.Items>
            <dxb:BarButtonItem x:Name="customNewFile"
                Command="{Binding FileNew, Mode=OneTime, Source={StaticResource commands}}"
                Content="Custom Create New File" />
            <dxb:BarButtonItem x:Name="customMergeCells"
                Command="{Binding EditingMergeAndCenterCells, Mode=OneTime, Source={StaticResource commands}}"
                Content="Custom Merge Cells" />
        </dxb:BarManager.Items>
        <Grid>
            <dxsps:SpreadsheetControl x:Name="spreadsheetControl1"
                BarManager="{Binding ElementName=barManager1, Mode=OneTime}"
                PopupMenuShowing="SpreadsheetControlPopupMenuShowing">
                <dxsps:SpreadsheetControl.MenuCustomizations>
                    <dxsps:SpreadsheetMenuCustomization MenuType="Cell">
                        <dxb:BarButtonItemLink dxb:BarItemLinkActionBase.ItemLinkIndex="0">
                            <dxb:BarButtonItemLink.BarItemName>
                                customMergeCells
                            </dxb:BarButtonItemLink.BarItemName>
                        </dxb:BarButtonItemLink>
                    </dxsps:SpreadsheetMenuCustomization>
                    <dxsps:SpreadsheetMenuCustomization>
                        <dxb:BarButtonItemLink dxb:BarItemLinkActionBase.ItemLinkIndex="1">
                            <dxb:BarButtonItemLink.BarItemName>
                                customNewFile
                            </dxb:BarButtonItemLink.BarItemName>
                        </dxb:BarButtonItemLink>
                    </dxsps:SpreadsheetMenuCustomization>
                    <dxsps:SpreadsheetMenuCustomization>
                        <dxb:BarItemLinkSeparator dxb:BarItemLinkActionBase.ItemLinkIndex="2" />
                    </dxsps:SpreadsheetMenuCustomization>
                    <dxsps:SpreadsheetMenuCustomization MenuType="ColumnHeading">
                        <dxsps:RemoveSpreadsheetCommandAction Id="{x:Static dxspscore:SpreadsheetCommandId.HideColumnsContextMenuItem}" />
                        <dxsps:RemoveSpreadsheetCommandAction Id="{x:Static dxspscore:SpreadsheetCommandId.UnhideColumnsContextMenuItem}" />
                    </dxsps:SpreadsheetMenuCustomization>
                </dxsps:SpreadsheetControl.MenuCustomizations>
            </dxsps:SpreadsheetControl>
        </Grid>
    </dxb:BarManager>

    <!--endregion #PopupMenuCustomization-->

</dx:DXWindow>