Change/configure 'start menu' icon
right-click icon → configure → use custom icon

Install arandr

sudo apt-get install arandr

Start it and save the screen state as a file.
Add the command in that file to /etc/lightdm/lightdm.conf.d/70-linuxmint.conf
i.e.

[SeatDefaults]
user-session=cinnamon

[Seat:*]
display-setup-script=xrandr --output DP-1 --primary --mode 1920x1200 --pos 1200x504 --rotate normal --output DP-2 --off --output HDMI-1 --off --output DP-2-1 --off --output DP-2-2 --mode 1920x1200 --pos 3120x0 --rotate left --output DP-2-3 --mode 1920x1200 --pos 0x0 --rotate left

Reboot system.

Terminal transparency setting as user. Get profile uid - only exists when settings changed once before, then set values:

export TMPUID=$(dconf dump /org/gnome/terminal/legacy/profiles:/ | grep "\[:" | sed 's/\[:\(.*\)\]/\1/')
dconf write /org/gnome/terminal/legacy/profiles:/:$TMPUID/use-theme-transparency false
dconf write /org/gnome/terminal/legacy/profiles:/:$TMPUID/use-transparent-background true
dconf write /org/gnome/terminal/legacy/profiles:/:$TMPUID/background-transparency-percent 9

#on new install, try:
dconf write /org/gnome/terminal/legacy/profiles:/:00000000-0000-0000-0000-000000000000/use-theme-transparency false
dconf write /org/gnome/terminal/legacy/profiles:/:00000000-0000-0000-0000-000000000000/use-transparent-background true
dconf write /org/gnome/terminal/legacy/profiles:/:00000000-0000-0000-0000-000000000000/background-transparency-percent 9