In Optimizely SaaS CMS there is no way to create an instance of a custom folder content type (a content type based on the folder / _folder base type) inside a shared block through the CMS UI. The New Folder action creates only the built-in system folder type and offers no picker to choose a custom folder type. Separately, the New Folder action is currently not working at all in this context. As a result, custom folder instances can only be created via the Content Management REST API or Opal.

Steps to reproduce:

1. Define a content type based on the folder (_folder) base type and push it to the CMS.
2. Open a shared block and go to the Assets panel.
3. Try to create a folder using New Folder.

Expected: The UI lets you create a folder of the custom folder type (e.g. a type picker), and the New Folder action works.

Actual: New Folder offers only the built-in system folder type — no way to select a custom folder type — and the New Folder option does not work in this context.

Impact: Editors can't self-serve folder organisation when custom folder types are involved — every folder creation needs a developer or an API call, which doesn't scale for content teams.

Request:

1. Fix the non-functioning New Folder action in the shared-block Assets panel.
2. Allow creating custom folder-type instances from the UI (a folder-type picker on New Folder), consistent with how other content types are selected.