How do I stop VSCode from the Side Bar moving to the folder that the current file is in?

The is an option explorer.autoReveal in settings (either user or workspace) which controls if the explorer should automatically reveal files when opening them.

1. Open VS User Settings (Preferences > User Settings). This will open two side-by-side documents.
2. Add a new "explorer.autoReveal": false setting to the User Settings document on the right if it’s not already there. This is so you aren’t editing the Default Setting directly, but instead adding to it.
3. Save the User Settings file.