Default Language for Plugin

Hi there,
I’m happily making use of the plugin. My entire site is built around it with code examples. I’m looking to make my life even a bit easier.

The default language for the plugin is ‘plain text’. How can I change this to be my preferred language?

I found this post with the PHP snippet, but it’s not working for me. Do you have an adjusted code for me?

https://www.ads-software.com/support/topic/how-to-set-a-default-language-parameter/