This tutorial shows the required steps to subtract the baseline.
Select data series 'Data' on left panel.
Select menu item
The dialog appears.
Click the [Operation] tab and select the operation 'Subtract', and then select the item 'Baseline modeling'.
New series appear.
Select the item 'Exclude points above the line' checked.
Vary the number of points in 'Window' to get best line.
Click the [Series] tab and select line color.
and close the dialog.