Currently Jenkins uses the Ace9 editor as its text editor for pipelines (and textarea for most other "big boxes"). I didn't do a deep dive on Jenkins source code, but searching around it seems I there is no support for plugins to modify or extend the pipeline text editor.

I believe it would be a net positive if we could write plugins to override the text editor. In particular, I'd like to use Microsoft's Monaco Editor over Ace9, as I feel it has a better feature set and looks better especially with Dark Mode. Since I couldn't find any plugin around - nor any plugin that changes text editors for that matter - I belive this means that Jenkins' text editor functionality aren't extensible at the present time.

So this ticket is a feature request to enable extensibility for the pipeline text editor and possibly other textareas(not sure if this is feasible).