Problem in defaults command when adding app with blanks in name to dock
Solution 1:
I recommend using dockutil for this. You can either download and install this directly from github, or you can install it using Homebrew with the command
brew install dockutil
Once installed, you can use a command like this to add an app with spaces in the path
dockutil --add '/Users/mac/Downloads/Yahoo News, Send & Weather2/YahooWeather.app'