Ive been using the online arduino IDE on mac high sierra and everything is fine. I bought a cheap nano, downloaded the ch340 driver and it worked swimmingly. I bought a esp8266 and read that it will only work on the downloaded software. But after downloading the software it only shows two ports /dev/cu.Bluetooth-incomming-port And /dev/cu.usbmodem1421(Arduino/Genuino Uno) And i cant get it to notice anyone of my three boards. the UNO, NANO or esp8266. ive also installed the nodemcu and SiLabsUSBDriver. Being a total noob ive tried a bunch of things not knowing if ive stuffed it up. So basically, the online IDE works but not the downloaded IDE.
I don't know the answer but I reckon it would help if you modify your Original Post and extend the Title to make it clear you are using a MAC.