Trouble with "escaping" characters

[ReaderGuy42]

I'd like to use this plugin to highlight LaTeX citing code, so e.g. \cite{Smith2020}. I'd like to permanently highlight everything between the \ and the }.

According to regexr.com this should work: (?<=\\)(.*?)(?=\}), i.e. it should highlight everything between a backslash \ and a }, so that \cite{Smith2020} would be highlighted.

The plugin doesn't like that though. When I do it via the GUI nothing happens, but when I try importing a highlighter, using the template from the github page:

{
  "TeX-Cite-highlight": {
    "class": "TeX-Cite-highlight",
    "color": "#77787C4A",
    "regex": true,
    "query": "(?<=\\)(.*?)(?=\})",
    "mark": [
      "match",
      "group"
    ],
    "css": ""
  }
}

I get the error: Error importing highlighters: SyntaxError: Unexpected token } in JSON at position 138.

So it seems that the escape character isn't read?

I've also tried this: \\(.*?)\} but with the same result. Again according to that regexr website it should work.

It's not just curly brackets btw. It also can't escape )

Any ideas?