How to Unhide System Startup Entries in Ubuntu
By default, Ubuntu hides the system’s default autostart entries in the “Startup Applications” dialogue. If you want to enable, disable, or remove any of these entries, you will need to unhide them before opening Startup Applications.
To unhide the system’s default entries, run this code in a terminal:
sudo sed -i ‘s/NoDisplay=true/NoDisplay=false/g’ /etc/xdg/autostart/*.desktop
Now your Startup Applications dialogue should look something like this:
To disable an option, uncheck its box rather than removing it. As these are system startup options, don’t disable something unless you know what it does.