Also, the thing is that whatever you edit in the /flash folder(s), will be wiped after a LibreELEC update or downgrade.
So perhaps doublecheck if you can use the /storage folder instead for whatever you are planning.
Video calibration settings should be stored in the guisettings.xml file, which is located in the /storage/.kodi/userdata/ folder.
Thanks Klojum, with a bit of trial and error managed to note settings needed for correct display then using nano entered settings directly in to guisettings.xml file.
Plus was totally unaware that /flash is mounted as read only but now able to deal with that.
An old 2USB Pi now able to receive TV streamed over the network. Technology, fascinating.
Geoff