Clear Clipboard on Mac

To force the clipboard app to restart on your Mac, you have to kill that process with the following instructions.

1. Launch Terminal

2. Run the following command:
   killall pboard

References
http://osxdaily.com/2018/02/02/fix-copy-paste-not-working-mac/

Add Dock Spacer on Mac

1. Start Terminal.

2. Run command to create spacer:
   defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="spacer-tile";}'

3. Reload Dock:
   killall Dock

4. Run the following commands below.

5. Close, re-open and re-run commands in step 1 in Terminal to add extra spacers.