Help on the js "flexsearch" script, theme: hugo-book

I usually do things on my own or ask for syntax questions so I admit it’s a bit embarrassing, but author of the theme isn’t very active, and the problem (more like a feature I would like to add) lies with the small (but important for the indexation/search module) js part of the site.
And I don’t know a single thing about js. You can find the files on the theme’s github.
Thoses, probably:

├──􀀂  assets 
 │  ├──􀆄  manifest.json 
 │  ├──􀆄  search-data.json 
 │  ├──􀀀  search.js 
 │  ├──􀀀  sw-register.js 
 │  └──􀀀  sw.js 
 └──􀀂  static 
    ├──􀀀  clipboard.js 
    ├──􀀀  flexsearch.min.js 
    └──􀀀  menu-reset.js 

don’t mind the precise directory though.
My wish, that when the search query’s first match lies in the page’s content, the search result gives an URL with text fragments, sending us directly to the part of the page that matches.
It’s probable simply but I don’t know ßðîþ about that language and learning would not be as easy as with goland, by far… so if someone feels like at least helping I would be thankful ;-i)

The “flex search” script are searching in the json file created here hugo-book/assets/search-data.json at master · alex-shpak/hugo-book · GitHub.

You get a permalink to the search hits but no way of knowing where on the HTML page that hit is.

yep, no way.