BAT. How to copy a part of a file starting from a certain line?

Question

cmd/bat

Data.txt

Вступление.
На несколько строк.

Заголовок нужных данных
Иванов
Петров
Сидоров
Васечкин

Result.txt

Иванов
Петров
Сидоров
Васечкин

There are text files of unknown size, the required information is at the end. It is preceded by a known string, for example, "Header of the required data". You need all the lines after the specified one (or together with it - it doesn’t matter) and append to the end of another file.
One of the possible solutions, but not complete. A working example from some amel27 to display the next line after the data start separator. I tried to repeat the last line increasing the counter and faced the fact that the script does not stop when it reaches the end of the file.

@echo off
set file=1.txt
set word=искомое слово

for /f "tokens=1  delims=[]" %%n in ('find /i /n "%word%" ^<"%file%"') do set /a "$n=%%n+1"
for /f "tokens=1* delims=[]" %%a in ('find /n /v "" ^<"%file%"^|findstr /b "\[%$n%\]"') do echo.%%b

My non-working version "on the forehead"

for /f "tokens=1  delims=[]" %%n in ('find /i /n "%word%" ^<"%file%"') do set /a "$n=%%n"
:doagain
set $flag1=1
set /a $n=%$n%+1
for /f "tokens=1* delims=[]" %%a in ('find /n /v "" ^<"%file%"^|findstr /b "\[%$n%\]"') do (echo.%%b & set $flag1=2)
if $flag1 leq 2 goto doagain

Answer 1

Added a little:

@echo off
set "file=1.txt"
set "search=Заголовок нужных данных"
set "header_line="
for /f "tokens=1  delims=[]" %%a in ('find /i /n "%search%" "%file%" ') do set "header_line=%%a"
if defined header_line (
  more +%header_line% "%file%"
)