Answer

Option 1: Add a total reference line

1. Right-click the Sales axis in the view and select Add Reference Line
2. In the Add Reference Line, Band or Box dialog, do the following and click OK:
   1. For Scope, select Per Cell
   2. For Value, select SUM(Sales) and Total
   3. For Label, select Value
   4. For Line, select None
3. Right-click one of the reference values in the view and select Format...
4. In the left-hand Format Reference Line pane, under Alignment, select Centre for Horizontal

Option 2: Create a dual axis graph with the stacked bar on one axis and the total/label on the other axis.

1. Create a new calculated field called "Total Sales per Category" and use the following formula:
   1. IF FIRST() = 0
      THEN SUM({FIXED [Category]: SUM([Sales])})
      END
2. Drag [Total Sales per Category] to the Columns shelf next to SUM(Sales)
3. Right-click on [Total Sales per Category] on the Columns shelf, and select Compute Using > Region
4. Open the [Total Sales per Category] the Marks Card and move Region from Colour to Detail
5. On the same Marks Card tab, change the chart type from Automatic to Gantt Bar
6. Right-click the NULL indicator in the view and select Hide
7. Create a new calculated field called "Percent of Total Label - Central" and use the following formula:
   1. SUM(
      IF [Region] = "Central"
      THEN [Sales]
      END)
       /
       SUM({FIXED [Category]: SUM([Sales])})
8. Drag [Percent of Total Label - Central] to Label on the [Total Sales per Category] Marks Card tab
9. Right-click on [Percent of Total Label - Central] on the Marks card and select Format...
10. Change the number format to Percentage.
11. Right-click on [Total Sales per Category] on the Columns shelf, and select Dual Axis
12. Synchronise the axis