I have an Odroid H4, with a spacious M.2 SSD, set up in a triple boot situation off the one disk, following manuals made by better minds than mine. It was a bit fidgetty but fairly straightforward in the end.
(first installed ubuntu, leaving room on disk, installed windows, still leaving some room on disk, reinstalled ubuntu over itself to fix bootloader, and then copied the libreelec partitions from an image of a working install on the machine into the empty space at the end of the disk, and finally hacked the grub bootloader in ubuntu to add libreelec and put it on top (where it belongs :), with windows as second option and ubuntu as third).
I have a kodi install auto starting in windows as well, so switching from LE to windows-kodi is seemless. And all my libreelec and kodi installs in the house share a library and highly customized minimal interface (arctic zephyr ftw) for a seemless user experience on all devices.
When i reboot the machine, grub auto boots into the top option LibreElec in 4 seconds. But if i want to reboot into the second (windows) or third (ubuntu) i have to make like a bomb disposal squad to find my keyboard to make the grub selection. When i reboot from Windows i dont have this issue because it autoboots to libreelec, and i know there are ways to tell ubuntu which grub option to boot into before rebooting.
Is there any way to add an option to boot into a second or third OS from the shutdown menu or thought some shortcut in LibreElec? So i can make the choice before rebooting and bypass the grub bootloaders detonation timer? Thanks in advance for any hints to achieve this.