How to remove the final backslash when quoting using a personalized heading?

Questions
2

@Jacu,

Could you please post code blocks using back ticks and not screenshots in order to better help you?

Could you please edit your (last two) post(s)?

``` 
#let x = … //code shows formatted
```

And ideally, your code should compile if pasted into a new .typ file. The example you have provided does not (because of #S not defined).

However, it looks like you are looking for How to properly set heading numbering to include supplement? - #5 by Andrew