#!/bin/bash
s="Section1
George, 1998-1995
Peter, 1999-1990
Simon, 1988-1960
Section2
Gery, 2019-2015
John, 1984-1983
Thomson, 1978-1965"
sed --posix -n '/^Section1$/ , /^Section[0-9]*$/{:a;h;n;/^Section[0-9]*$/!ba;x;s/^[ \t]*//;p}' <<< "$s"
IyEvYmluL2Jhc2gKcz0iU2VjdGlvbjEKICAgIEdlb3JnZSwgMTk5OC0xOTk1CiAgICAgUGV0ZXIsIDE5OTktMTk5MAogICAgIFNpbW9uLCAxOTg4LTE5NjAKU2VjdGlvbjIKICAgICBHZXJ5LCAgMjAxOS0yMDE1CiAgICAgSm9obiwgIDE5ODQtMTk4MwogICAgIFRob21zb24sICAxOTc4LTE5NjUiCnNlZCAtLXBvc2l4IC1uICcvXlNlY3Rpb24xJC8gLCAvXlNlY3Rpb25bMC05XSokL3s6YTtoO247L15TZWN0aW9uWzAtOV0qJC8hYmE7eDtzL15bIFx0XSovLztwfScgPDw8ICIkcyI=