Hi VinceBokk,
That codeblock option can be found in the Note editor -> Add (the blue circle/+) dropdown (where also the options are to add a table, checkbox etc.). What it does is to format the text that you enter as code. Hope this helps.
Bert
In the Dutch translation of the Note editor -> Add -> Code block is incorrect. The correct translation is "Codeblok" (noun) instead of "Codeblokkeren" (=verb).