Buttons and menus are named exactly as the app shows them.
Steps
Pick a mode
Choose Countdown, Count-up or Stopwatch.
Where: Clock tab › Timer
Run more than one
Start another timer while one is running. Each keeps its own time.
Move around freely
A running timer follows you through the app. It remembers when it started, so it is right when you come back from another app or a locked screen.
Let sessions log themselves
With Auto-log timer sessions on, a finished focus session becomes an entry by itself.
Where: Settings › Preferences