You need to expand the transformer parameters first and then right-click on one of them. Does this example screenshot explain it better?

Here's an alternative way to do the same thing:

Hi @allensong,

Rather than right clicking on the Transformer name itself you will need to expose the list of parameters belonging to that transformer. Right click on the single parameter that you would like to create a user parameter for and then the option should appear:

Thank you for quick response, I found it, really appreciate.