Add spacer to MacOs Dock

Run the command in terminal and spacer is added to the Dock automatically.

Add spacer to block

defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="spacer-tile";}'; killall Dock

Add small spacer to Dock

defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="small-spacer-tile";}'; killall Dock