Add Vertical Line to Line Chart based on one Value

I have a line chart consisting of two categories. The x-axis contains dates (as texts) and the y is an average probability. I want to add a vertical line (red dotted line) to the chart based off of a value from a column (10/1/20). The column has one value for all rows. I can't insert a red line at 10/1 because I have several slicers attached to the visual that will cause the dates to move around. Any ideas or workarounds?