Goodmorning everyone,
I have been using WordPress for 3 years and today I would like to ask for help on a topic that is absent in the Italian documentation (I apologize if not, I have searched a lot!). I come straight to the point: how can you change the text of the search bar (called ‘Search’ in widget) on the side?

I know I have to enter some code string but I ignore the contents of the code.
I tried a lot of different codes but they doesn’t work. Not even with “My Custom Functions” plugin.

Thanks for help!