When creating an expression function, choose the text displayed in events sheet

I’ve created an extension called “extensionname”. Inside I am creating an expression called “functionname”, (with 2 parameters)

As you can see, in the events sheet, my expression is displayed as " extensionname::functionname "

How could I choose the text displayed here ?

(Like if I use the “Search in a text” expression, then in the events sheet it doesn’t display " textmanipulation::searchinatext ", but it displays " StrFind ")