Couldn’t find a more suitable section to request a syntax highlighting for .ovpn files

This forum is for discussion, not for feature requests. If you explore the Forum, you will easily find the FAQ section of this Forum, which has an entry called “FAQ Desk: Feature Request or Bug Report”: that FAQ entry tells you how to make a Feature Request.

That said, Notepad++'s built-in syntax highlighting (like the C++, HTML, Python, etc) are inherited from the Scintilla project (Notepad++ uses some Scintilla IP under the hood); Scintilla long ago stopped adding new built-in syntax highlighters, so Notepad++ hasn’t added new built-in highlighters in quite some time.

At this point, the Notepad++ developers encourage users to make use of one of two existing features of Notepad++ to get more syntax highlighting:

1. Notepad++ comes bundled with the User Defined Language (UDL) system, where you can define your own simple keywords and comment syntax for syntax highlighting, code-folding, and the like. This is the most-commonly used feature for defining your own syntax highlighting
2. Notepad++ has the capability to accept plugins, and it’s possible to develop a lexer / syntax highlighter plugin – fewer have made use of this, but you can see at least one in the Plugins Admin called “GEDCOM Lexer”

My guess, since it’s a config-file syntax, is that UDL will serve your needs. It’s not really that hard to get started writing your own UDL.