Trilium supports creating “code” notes, i.e. notes which contain some sort of formal code - be it programming language (C++, JavaScript), structured data (JSON, XML) or other types of codes (CSS etc.).
This can be useful for a few things:
Trilium supports syntax highlighting for many languages, but by default displays only some of them (to reduce the number of items). You can add extra languages in Options -> Code notes.
An alternative to the code note is a “code block” - feature of a text note which can add short snippets of code to the text editor. The disadvantage is that code blocks don’t support syntax highlighting.