Scanning on the 779UV is a tad quirky since you can only initiate scanning from the microphone keypad. You must press the ‘F‘ key and the ‘4/scan’ key in order to start scanning. Kind of inconvenient in a mobile setting. There is no way to start/stop scanning from the radio itself.
You can lock out a channel, but again, it is done through the mic keypad by pressing the ’F’ key and then the ‘3/Skip’ key.
However, when you are scanning and want to skip a channel by starting the sequence of ‘F then 3’, the radio will return to the channel it started on, not the current busy channel, so you must pay attention to the channel you would like to lock out.
So yes, you can add or remove channels from the scan function via the mic keypad.