Issue can be resolved by disabling the SIP on macOS High Sierra and then installing CH34x_Install_V1.5.pkg. I can now detect the Maker-UNO, Maker-Nano and UNO-CH340 on my MacBook (macOS High Sierra)

disable System Integrity Protection:
  • Reboot your Mac into Recovery Mode by restarting your computer and holding down Command+R until the Apple logo appears on screen.
  • Open the Terminal (Applications > Utilities > Terminal).
  • In the Terminal window, type in csrutil enable --without kext (or to fully disable: csrutil disable) and press Enter.
  • Restart your Mac.

ref:  https://github.com/adrianmihalko/ch340g-ch34g-ch34x-mac-os-x-driver