Using relationships: You can use relationships to link the secondary data source with the primary data source based on a common field. This will allow you to use fields from both data sources in your visualization without creating new fields or duplicating data. You can then replace references to update the dimension values. For example, you can use relationships to link the updated dorm codes with the primary data source and then replace Dorm_Code with Dorm_Code_New in your visualization.
https://community.tableau.com/s/question/0D54T00000C5ldZSAR/update-data-view-based-on-dimension

To connect a Tableau workbook to a dataset in a Microsoft Excel spreadsheet, you need to select New Data Source from the Data menu. This will open the Connect pane, where you can choose Microsoft Excel as your data source and browse for your spreadsheet file. You can then drag and drop your sheets or tables to join or union them in the data source page. Reference: https://help.tableau.com/current/pro/desktop/en-us/connect_basic.htm https://help.tableau.com/current/pro/desktop/en-us/connect_excel.htm

When you sign in to a Tableau Server site from Tableau Desktop and search for a published data source, you will see all the data sources published to the site within the folders to which you have access. You will not see data sources published to other sites or folders that you do not have permission to view. You can also filter your search by project, owner, or tag. Reference: https://help.tableau.com/current/pro/desktop/en-us/connect_basic.htm https://help.tableau.com/current/pro/desktop/en-us/connect_tableauserver.htm

To combine the lines to appear as shown in the second chart, you should set Discount to Dual Axis. Dual Axis is a feature that allows you to show two measures on two separate axes on one chart. You can create a dual axis by right-clicking on a measure on any shelf and selecting Dual Axis from the menu. This will create two axes on one chart and synchronize their scales.
In this case, you want to show Profit and Discount on two separate axes on one chart. You can right-click on Discount on any shelf and select Dual Axis from the menu. This will create a dual axis chart that shows Profit and Discount as two lines with different colors.
The other options are not correct for this scenario. Dragging Discount to Color on the Marks card will change the color of Profit based on Discount, but it will not show two lines. Converting Discount to Discrete will change Discount from a green pill to a blue pill, but it will not affect how it appears on the chart. Dragging Discount to Columns shelf will create two separate charts for Profit and Discount, but it will not combine them. Reference: https://help.tableau.com/current/pro/desktop/en-us/multiplemeasures.htm https://help.tableau.com/current/pro/desktop/en-us/multiplemeasures_dualaxes.htm