Since your graphs are just straight line segments, you could overlay them with path by just putting path anchors on the angle points (24 points per line). Then you would use Edit > Stroke path to stroke the lines, in Line mode when you can use various dot patterns (and even define your own). You can also stroke the same path before hand in Tool mode with the erase to erase the existing line before restroking.
However... it would be about as fast and give a much cleaner result to use the Measure tool to measure the distance between each point and the X axis, enter that in a spreadsheet, apply a scaling factor, and recreate the curves with the dotted lines you want directly with the spreadsheet app.
However... it would be about as fast and give a much cleaner result to use the Measure tool to measure the distance between each point and the X axis, enter that in a spreadsheet, apply a scaling factor, and recreate the curves with the dotted lines you want directly with the spreadsheet app.