Hi, this may sound silly but as a newbie to LibreELEC i chose to runs the initial installation from a USB to get a feel for it - choosing "live", then "run" from boot. Thankfully after setting up and testing the system LibreELEC appears to meet my needs so I decided to install it to the PCs SSD.
Having spent quite some time setting up the installation on the USB I wanted to transfer that installation to the hard disc. I initially did this by cloning the USB to the SSD but that still left the installer/live/run question on boot. So I decided to do a proper install and chose "installer", that went well but unsurprisingly created a clean install. No worries, I decided to recursively copy the .kodi directory on my USB to the .kodi directory on the SSD. Unfortunately that didn't work as planned and the new SSD installation remained "virgin". So I had to repeat setting up the system.
Bottom line: all is well but it would be nice to have the option to "clone" an experimental installation to become a permanent one during installation.