VSCode showing only one file in the tab bar (can't open multiple files)

On a mac, if both of the existing answers didn't work, you can try command + ctrl + w, worked for me.

Check User interface / Tabs. You just need to add the following line in the configuration file.

"workbench.editor.showTabs": false

I also think that How do I disable tabs in Visual Studio Code? is asking the exact opposite of what you are asking.

The accepted answer didn't work for me for some reason. The answer given in Open files always in a new tab did.

In short: In the menu bar, click on File > Preferences > Settings. Then add the following line to the settings file.

"workbench.editor.enablePreview": false