I spent way too long looking for this shortcut today. Lots of people suggest Ctrl+Alt+Backspace, the traditional X restart combination, but it doesn’t work for me in Cinnamon. Others suggest CLI methods, which is fine, but not what I was after. I knew there was a shortcut that reloaded the desktop without interrupting anything running.

Ctrl+Alt+Esc is the one that does this.

Thanks to a downvoted answer on this thread.