In Visual Studio Code, a while ago, when I used menu View → Split Editor, it would split vertically. (One file on the left and one file on the right.)

I updated Visual Studio Code and when when I do menu View → Split Editor, it always splits horizontally. (One file on the top and one file on the bottom.)

How can I split vertically?

Change editor split layout from horizontal to vertical

In 1.20

• ALT+SHIFT+0 PC (Windows, Linux)
• ⌘+⌥+0 Mac

Pre-1.20

• ALT+SHIFT+1 PC (Windows, Linux)
• ⌘+⌥+1 Mac

In 1.25

• You can split editor into Grid layout. Check View=>Editor Layout
• It is nicely presented in Release notes v1.25: VS Code grid editor layout

In 1.58.2 **

** Someone update this with the lowest version where this became true.

• The menu entry with the shortcut given above is View=>Editor Layout=>Flip Layout
• The Command Palette entry is labeled "Toggle Vertical/Horizontal Editor Layout"
• The settings entry is

  {
    "key": "alt+cmd+0",
    "command": "workbench.action.toggleEditorGroupLayout"
  }