It would be nice to be able to filter the extension list by publisher.

Per this resource, VS Code Marketplace offers this:

1. In IDE:

2. On Web: https://marketplace.visualstudio.com/search?term=publisher%3Amicrosoft&target=VSCode&category=All%20categories&sortBy=Relevance