<ScrollViewer HorizontalScrollBarVisibilitty="Auto" VerticalScrollBarVisibility="Auto">
    <TabControl>
        <TabItem>
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="300"/>
                    <ColumnDefinition/>
                </Grid.ColumnDefinitions>
                <StackPanel>
                        <!-- Main Content, allow horizontal scrolling, don´t allow vertical scrolling-->
                </Stackpanel>
                <StackPanel Grid.Column="1">  // Allow Vertical Scrolling
                     <Expander>
                            <!-- Description 1 -->
                     </Expander>                     
                     <Expander>
                            <!-- Description 2 -->
                     </Expander>                     
                     <Expander>
                            <!-- Description 3 -->
                     </Expander>                     
                </StackPanel>
            </Grid>
        </TabItem>
        ...
    </TabControl>
</ScrollViewer>