Thanks for the suggestions. The solution I came up with can be seen at https://github.com/intersystems-community/vscode-per-namespace-settings

It installs a class, runs a method in it to create the web app so it uses the correct namespace, then deletes the class. Actually, it deletes a whole package which I named %Z.IPM.Bootstraps with the idea that this could be by convention a package reserved for exactly this purpose.

I had to devise a little hack to prevent the deletion from happening during packaging, otherwise the web-app-creating class wouldn't actually be in the package, meaning end-user installation would fail.

Maybe there's already a better way of achieving the effect I wanted.

Since you are working client-side I think you need to set a intersystems.testingManager.client.relativeTestRoot setting to contain the workspace-relative path to the tests folder that's showing at the beginning of the breadcrumb in your screenshot.

Please see point 2 of https://github.com/intersystems-community/intersystems-testingmanager#wo...

Thanks for the positive response. IMO the main thing needed before the Preview tag gets dropped is feedback from %UnitTest users.

One motivation for publishing the Preview is the upcoming Global Summit, which I hope will be a good opportunity for in-person discussion about this extension and others. Find me at the George James Software booth in the Partner Pavilion. 

Outline information is always available in the CHANGELOG, and instead of waiting for a post here I suggest you configure VS Code to check for extension updates without installing them automatically. That way you'll know when you update this extension, and it's easy to review the CHANGELOG in Extensions view afterwards.

I think there's also a Discord channel that notifies about releases.