/usr/share/live/images/lxde-desktop/config/bootloaders/pxelinux/install.cfg is in live-image-lxde-desktop 4.0~a5-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | label install
menu label ^Install
menu default
linux /install/vmlinuz
initrd /install/initrd.gz
append vga=788 @APPEND_INSTALL@ -- quiet
label installgui
menu label ^Graphical install
linux /install/gtk/vmlinuz
initrd /install/gtk/initrd.gz
append video=vesa:ywrap,mtrr vga=788 @APPEND_INSTALL@ -- quiet
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