Press ⇧⏎ (macOS) / Shift+Enter (Windows/Linux) to start a new line. You can do this at the start of a line, the middle of a line or the end of a line, the indentation will always be correct. Alternatively, to start a new line above your current line of code, you can press ⌘⌥⏎ (macOS) / Ctrl+Alt+Enter (Windows/Linux).