Remap tilde and left shift on a UK keyboard

remap.sh

hidutil property --set '{"UserKeyMapping":[{"HIDKeyboardModifierMappingSrc":0x700000035,"HIDKeyboardModifierMappingDst":0x7000000E1}, {"HIDKeyboardModifierMappingSrc":0x700000064,"HIDKeyboardModifierMappingDst":0x700000035}]}'

cat << 'EOF' > ~/.keymappings && chmod +x ~/.keymappings
hidutil property --set '{"UserKeyMapping":[{"HIDKeyboardModifierMappingSrc":0x700000035,"HIDKeyboardModifierMappingDst":0x7000000E1}, {"HIDKeyboardModifierMappingSrc":0x700000064,"HIDKeyboardModifierMappingDst":0x700000035}]}'
EOF

sudo /usr/bin/env bash -c "cat > /Library/LaunchDaemons/org.custom.keymappings.plist" << EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>org.custom.keymappings</string>
    <key>Program</key>
    <string>${HOME}/.keymappings</string>
    <key>RunAtLoad</key>
    <true/>
    <key>KeepAlive</key>
    <false/>
  </dict>
</plist>
EOF

sudo launchctl load -w -- /Library/LaunchDaemons/org.custom.keymappings.plist