Is it possible to use the vscode: hyperlink to open a file or directory in Code?

Yes, it is possible.

Open a project (or a directory)

vscode://file/{full path to project}/

vscode://file/c:/myProject/

Open a file

vscode://file/{full path to file}

vscode://file/c:/myProject/package.json

Open a file to line and column

vscode://file/{full path to file}:line:column

vscode://file/c:/myProject/package.json:5:10

More details: https://github.com/Microsoft/vscode-docs/blob/master/docs/editor/command-line.md#opening-vs-code-with-urls