I have a dashboard with a line chart. When the dashboard loads, I intend to highlight a data point based on the x-axis value. This value would be present in the URL as a query parameter.
Should be fairly simple to do
In Tableau create the graph and a parameter to control the highlight. Publish the graph to Tableau Server then create the URL that includes the parameter value and the graph renders as you require.
Which part of that do you need help with though ?