[GNC] Scheme Report - SubTotals to Normal Style with Hidden Transactions

[flywire]

The Transaction report has an option to hide transaction data and just
report Account totals; Option, Sorting, Show subtotals only (hide
transaction data). Prefixing all lines with "Total for " and highlighting
them makes the report harder to read.

I tweaked
https://github.com/Gnucash/gnucash/blob/4.13/gnucash/report/trep-engine.scm#L1600
to suppress the prefix when transaction data is hidden as shown in the code
below. I'd like to use the option setting to suppress the highlighting too.
Can someone tell me how to change the variable? I can work it into an
appropriate condition line later. My failed attempt is commented out in the
last line:

    ; (define (total-string str) (string-append (G_ "Total For ") str))
    (define (total-string str)
      (if (opt-val pagename-sorting optname-show-subtotals-only)
        str
        (string-append (G_ "Total For ") str)))

    ; (set! def:primary-subtotal-style def:normal-row-style)