I run LibreELEC from one of my systems from an SD Card, retaining the original Android OS on the NAND memory, so I can Dual-Boot.
It was just pointed out to me that there is a ‘Reboot to Nand’ option in the Shutdown menu of the LibreELEC Confluence Skin;
I had never noticed it because as soon as I install a new system, I switch to BGN 
That option just does not appear in BGN so I was oblivious to it.
I created a new image of LibreELEC and left it in the Confluence Skin and sure enough, it is right there as one of the options in the Shutdown menu.
It’s not part of the BGN menu as-is, but obviously the capability is there within the LibreELEC OS:
How can I create a sub-menu command to utilize “Reboot to NAND” ?
It would really be most useful to have this.
This would be applicable for both BGN v5.x and v6.x