If your visualization has a table calculation and you'd like the extension to use that table calculation as one of its measures in addition to the measure the table calculation was derived from, follow the steps below!
1. Start by making your table calculation
2. Drag your table calculation into the measures on the left-hand side panel
3. Name your new calculated field (i.e. the table calculation you just made)
4. Drag your original measure (Sales) back to the top and pull your calculated field into the tooltip. This will allow your visualization to remain the same (Total Sales by Segment) but still gives you access to the new measure (Percent of Total Sales).
5. Now when you go to your dashboard with this sheet and pull on the extension, you'll see in the second step of the extension set up that the narrative has access to both measures.