What is Ctrl + K for?
Ctrl + K opens the palette: a single box to search, but also to run an action by typing its name.
Step by step
Press Ctrl and K at the same time. The palette opens in the middle of the screen.
Before you type anything, it suggests actions (write a message, create a task…) and your recent files.
Type a few letters: it searches your messages, files and contacts, and the actions.
Choose with the arrow keys and Enter, or with a click. Esc closes it.