If you want to just disable that one shortcut, then simply execute these 2 lines:
mkdir -p ~/.config/xfce4/terminal
echo ‘(gtk_accel_path “<Actions>/terminal-window/contents” “”)’ >> ~/.config/xfce4/terminal/accels.scm
Close all instances of xfce4-terminal to apply the change.
xfce4-terminal opens its help when pressing F1. The process to change that is *censored* – see here:
What this means is:
Open Settings/Appearance, then goto tab “Settings” and check “Enable editable accelerators”.
Then in xfce4-terminal, click “Help” and hover over “Contents F1”. Press backspace or delete.
For safety, disable the “Editable accelerators” again.
This creates the file ~/.config/xfce4/terminal/accels.scm, which seems to contain all keyboard shortcuts.
But having just the shortcuts that you want to change in there seems to work as well.