Feature Request: simple syntax highlighting for timelion

[SolomonShorser-OICR]

Feature Request

Sometimes working with Timelion can involve several series that have some complex queries. After a while, complex queries get hard to read.

It would be nice if there were some sort of simple syntax highlighting to make it easier for the eye to pick out different parts of a Timelion query. There's a Timelion tutorial here: https://www.timroes.de/2017/08/02/timelion-tutorial-from-zero-to-hero/ that has syntax highlighting, although I think it's a more generic highlighter. Timelion could benefit from more specific highlighting (in addition to more generic highlighting that would help distinguish strings from numbers from keywords...). Timelion-specific highlighting I was thinking of could be different classes of functions highlighted in different colours.
Example: functions that calculate derivative could highlight differently than functions that affect the visual display such as colour, bars/lines, etc...

[timroes]

Actually a duplicate of #12075, but since you added a better description (and of course linked to my blog ;D) I will leave this one open.

The syntax highlighting for timelion is actually a timelion "specific" one I wrote for highlight.js (https://github.com/timroes/www.timroes.de/blob/master/gulp/rendering/languages/timelion.js).
Though highlight.js cannot be used for input fields. I still find the general idea nice, to have a specific syntax highlighter. I think since we have a long running effort to maybe have a better code editor in EUI (elastic/eui#499) I would wait for any progress or outlook there, before we look into writing some syntax highlighting.

[stratoula]

Thank you for contributing to this issue, however, we are closing this issue due to inactivity as part of a backlog grooming effort. If you believe this feature/bug should still be considered, please reopen with a comment.