When using a custom user data directory with vscode like in the example below, vscode-coder fails to open the workspace.(see below image)
Example: code --user-data-dir=u:\test\user-data --extensions-dir=u:\test\ext-dir
Please note that creating a directory at  %appdata%\Code\User seems to solve the issue but I think the extension should use the custom user data directory instead in this case.