1. Multi cursor selection
To add cursors at arbitrary positions, select a position with your mouse and use Alt+Click(Option+click on macOS).
To set cursors above or below the current position use:
Keyboard Shortcut: Ctrl+Alt+Up or Ctrl+Alt+Down
You can add additional cursors to all occurrences of the current selection with Ctrl+Shift+L.
If you do not want to add all occurrences of the current selection, you can use Ctrl+D instead. This only selects the next occurrence after the one you selected so you can add selections one by one.
2. Column (box) selection
You can select blocks of text by holding Shift+Alt (Shift+Option on macOS) while you drag your mouse. A separate cursor will be added to the end of each selected line.
3. Copy line up / down
Keyboard Shortcut: Shift+Alt+Up or Shift+Alt+Down
4. Move line up and down
Keyboard Shortcut: Alt+Up or Alt+Down
5. Shrink / expand selection
Keyboard Shortcut: Shift+Alt+Left or Shift+Alt+Right