One solution would be to create a parameter (let's call it Select ID) and set up that parameter to be populated from the ID Number field.
Then you can create a calculated field, which I'll call Selected ID Sample, with the following definition:
// Measure will only show the sample for the selected ID.
IF [ID Number]=[Select ID] THEN
Then add that to to the list of measures and you'll get something like this:
This will give you just a single dot because this axis is set as a line chart. If you want this to show as an X or some other shape, then instead of adding it to your measures, drag it up next to Measure Values on the rows shelf:
Then make that a dual axis and be sure to right click on the y-axis and choose "Synchronize Axis".
At this point, it still looks the same as the original, but since we have two axes now, we can make the second one a different type of chart. So click on the second axis and change it to a Shape mark type. You can then change the shape as desired.
The attached workbook has both options on two separate sheets.
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TEST overlay.twbx 58.8 KB