Assuming you’ve created a chart that you want to add this highlight to, put the newly-created calculated field on the opposite axis to create a dual-axis chart (learn how to create a dual-axis combo chart in Tableau).
In my case, the original chart was a histogram with a mark type of area. When I put the new calculated field on the opposite axis, it inherits the same mark type as the original chart by default. Here is how my view looks at this point (note that I have also selected to show parameter control which makes it appear in the top right corner):
From here, there is just a little cleanup to make a nice highlight/reference band effect:
Fix the axis of the right axis by right-clicking on the axis and choosing "edit axis." For the best results, fix the axis at a number smaller than the number in your newly created calculated field (mine is fixed at 1, which is less than 1.5).
Change the mark type of the second axis to bar, which will create the band look.
Change the format of the bars to the size and color that you want. I recommend adding borders and transparency.
Hide the headers for your second axis by right-clicking on the axis and unchecking “show header."
My final product looks like this:
Now if the name of the dimension member matches the parameter selection, you will see a nice highlight of that choice on the x-axis—a reference band on a dimension in just three steps!
For more tips, tricks, and works by Ryan Sleeper, visit his Tableau public page and read his blog posts on Evolytics.com.