Indeed, there is a way to show the dB reference for pressure (sound) in Test.Lab displays, using the LMS Units Editor. Below is a screen-shot showing the result in a Test.Lab display. We hope this is what you are looking for.
Included below are the steps on how it is done:
In the Units Editor, perform a search (Ctrl+F) for the word ‘Pressure’ and check the box for “Match whole words”. This will take you to the Quantity case Pressure with Unit Case label Pa, i.e., the default one.
Double click on that row (Pressure | Pa | Default), which will open a new window.
In this window, edit the ‘Level Label’ to include the text for reference the way you would like it to be. The default one is dB<W> but you could change it to 'dB <W> ref 20E-06'. Press OK when done.5. Save the new units file through 'File -> Save' then do 'File -> Exit'
Open Test.Lab project to confirm that reference value is being displayed for Pressure data in the displays.
Note that this units file change is done in the LMS Units Editor, so it is outside of Test.Lab. So all your displays in any project will automatically show the newly added reference value(s).