Enter presentation mode via shell script placed in the dock.
- Type "caffeinate" and save as plain text file with name "caffeinate.sh".
- Set file executable in the Terminal with "chmod a+x drag_here_your_file_caffeinated.sh".
- File » Open With… » Other: Terminal.
Open shell script to prevent Mac from sleep. Close Terminal to allow Mac to sleep. Drag the file to the Dock if you like.
Background: Apple provides a Terminal command called "caffeinate". Type "man caffeinate" in the terminal to see the options. Quit man with q key.