For an easy maintainable Arduino-esp8266-ide I do something like:
a) download:
recent (1.8.6 recc.) Arduino-ide as .zip version (https://www.arduino.cc/en/Main/Software)
attached "package_esp8266com_index.txt" and rename to .json
b) unpack Arduino to suitable place (e.g. d:\arduino, keep the version info if you like to have several versions)
add "package_esp8266com_index.json" to this directory
c) create an empty directory "portable" in this directory
d) start Arduino, goto "file/preferences" and add "file://d:/arduino/package_esp8266com_index.json" to
"Additional Boards Manager URLs:", hit "OK" (restart Arduino)
e) goto Board Manager and install the Versions you want/need
f) quit Arduino to make some helpfull modifications:
1) under ...\portable\packages\esp8266\hardware\esp8266_XYZ\X.Y.Z\ edit all platform.txt:
(not necessary for >2.4.2 or git after 8/18)
change line "name=ESP8266 Modules" to e.g. "name=ESP8266 2.3.0 Modules" to reflect the version= given in the next line
(this is what you see as sectionheader in the board selection list)
2) for the platform.txt of the git version (...\portable\packages\esp8266\hardware\esp8266_git\X.Y.Z) you
also have to additionally modify the following lines (see also attached example):
#runtime.tools.xtensa-lx106-elf-gcc.path={runtime.platform.path}/tools/xtensa-lx106-elf
#runtime.tools.esptool.path={runtime.platform.path}/tools/esptool
tools.esptool.path={runtime.tools.esptool.path}
tools.mkspiffs.path={runtime.tools.mkspiffs.path}
If later you want to update to newer .git version, just goto boardmanager, remove git-version and reinstall it (don't forget modifications to platform.txt!).
this gives you the freedom of the location of your Arduino-ide, simplifies backups (all in one dir) and parallel ide versions, keeps your settings, all sketches and additional libs in one place (portable\sketchbook)
p.s.: you can safely download and use package_esp8266com_index. If you have a look at it, you will see that the changes are obvious and just work around ArduinoIDEs problem not allowing several versions for same hw plattform (disguising each version as different plattform of same board manufacturer).
Plus adding an section for the git version.
p.p.s.: if the ide won't start up after changes, chances are high that you removed last selected board.
fix: open preferences.txt and clear entries for
target_package=
target_platform=
Edit: included 2.4.2