Use the following workaround to display months only for Q3.

Step 1: Create a Parameter

1. In Tableau Desktop, connect to the Superstore sample data.
2. Right-click in the Data window and then select Create Parameter.
3. In the Create Parameter dialog box, do the following, and then click OK:
   • Name the parameter. In the example workbook, the parameter is named Quarter.
   • For Data Type, select Date.
   • For Allowable values, select Range.
   • Click the boxes next to Minimum and Maximum, and keep the default values.
   • Click the box next to Step size, select 1, and then select Quarters from the drop-down list.
4. Right-click the new parameter and then select Show Parameter Control.

Step 2: Create a Calculated Field

1. Select Analysis > Create Calculated Field.
2. In the Calculated Field dialog box, do the following, and then click OK:
   • Name the calculated field. In the example workbook, the calculated field is named Telescope Months.
   • In the formula field, create a calculated field similar to the following:
     IF DATEPART('quarter',[Order Date])=DATEPART('quarter',[Quarter]) 
THEN DATENAME('month',[Order Date])
ELSE "ALL"
END

Step 3: Build the View

1. Drag Order Date to Rows.
2. On Rows, right-click YEAR(Order Date), and select Quarter (Q2).
3. Drag Sales to Columns.
4. Drag Telescope Months to Rows.