For a Pipeline job

• mark This project is parameterized and add any string parameter with a given value, say secret1

  example_string=secret1
  

• add pipeline description

  #!groovy
  def specialPlatformTestDir
  
  specialPlatformTestDir = 'secret2'
  echo specialPlatformTestDir
  
  specialPlatformTestDir = 'secret1'
  echo specialPlatformTestDir
  

After the job execution, you will see in Blue Ocean view that it hides "secret1" in steps but shows "secret2":

It will behave the same way for any pipeline step: strings which contain a parameter value will be hided