How can you launch VSCode with multiple extensionDevelopmentPath sources?

I'm trying to test local changes of omnisharp-vscode in conjunction with my own local extension. I can't for the life of me figure out how to boot the VSCode experimental instance with more than 1 extension.

I've tried:

• Providing multiple extensionDevelopmentPath arguments when booting vscode
• Running omnisharp-vscode and then opening and running my other extension in the experimental instance.

None of the above have worked for me.

The easiest solution would probably be to simply move one (or both) extensions into your .vscode/extensions directory. This might require you to remove the marketplace installs of those extensions if present. Even though "development installations" of extensions like this are not officially supported yet, they work just fine regardless.