There are a couple different ways that you can show an outline in Excel.
One way is to use the Outline feature. To use this, first select the data that you want to include in your outline. Then, go to the Data tab on the ribbon and click on the Outline button. This will show a basic outline of your data.
If you want more control over your outline, you can use the Group feature. To use this, first select the data that you want to include in your outline. Then, go to the Data tab on the ribbon and click on the Group button. This will bring up a menu where you can choose how you want to group your data.
You can also use the Subtotal feature to show an outline of your data. To use this, first select the data that you want to include in your outline. Then, go to the Data tab on the ribbon and click on the Subtotal button. This will bring up a menu where you can choose how you want to summarize your data.
Finally, you can use the PivotTable feature to show an outline of your data. To use this, first select the data that you want to include in your outline. Then, go to the Insert tab on the ribbon and click on the PivotTable button. This will bring up a menu where you can choose how you want to organize your data.