Use ⌃` (macOS) / Ctrl+` (Windows/Linux), to bring up the Quick Switch Scheme dialog.

You can use the arrow keys to navigate to View Mode and select it to see list of view modes available. Alternatively you can press the number of that option in the list. Next, use the arrow keys to navigate to Enter Distraction Free Mode or press 2 to select that option, to display just your editor window and focus on coding.

Alternative Ways of Entering Distraction Free Mode

Using the main menu

You can use the menu View | Appearance | Enter Distraction Free Mode.

Using Search Everywhere

Use ⇧⇧ (macOS) / Shift+Shift (Windows/Linux), to bring up the Search Everywhere dialog. You can now search for Distraction and select Enter Distraction Free Mode.

Exiting Distraction Free Mode

When you're Distraction Free Mode, use any of the above-mentioned ways to exit Distraction Free Mode.

Using the Quick Switch Scheme

Open the Quick Switch Scheme dialog ⌃` (macOS) / Ctrl+` (Windows/Linux), and select View Mode followed by Exit Distraction Free Mode to exit distraction free mode.

Using View Toolbar Options

Alternatively, you can also use the menu View | Appearance | Exit Distraction Free Mode.

Using Search Everywhere

Use ⇧⇧ (macOS) / Shift+Shift (Windows/Linux), to bring up the Search Everywhere dialog. You can now search for Distraction and select Exit Distraction Free Mode.

Alternatively, you can use ⌘⇧A (macOS) / Ctrl+Shift+A, to bring up the Find Actions dialog which will filter the Search Everywhere dialog to just Actions.