It's not possible to add items to Collection block - they can be selected in UDW, but they are not displayed on the items list.

Setup:
A working Collection Block configuration.
Example:
Add those two files to corresponding folders in studio-ui-bundle: https://github.com/ezsystems/ezstudio-demo-bundle/pull/196 (change eZStudioDemoBundle to eZStudioUIBundle).

Add these lines to eZStudioUIExtension.php

$configFile = __DIR__ . '/../Resources/config/default_layouts.yml';
        $config = Yaml::parse(file_get_contents($configFile));
        $container->prependExtensionConfig('ez_systems_landing_page_field_type', $config);
        $container->addResource(new FileResource($configFile));

They should be added above:

     $this->prependYui($container);
     $this->prependCss($container);

Steps to reproduce:
1. Create two Articles in the Content section
2. Create a new Landing Page
3. Add a Collection Block
4. Open Block, click "Select Content"
5. Add articles added in Step 1, Confirm selection

Expected:
Articles are displayed in the list

Actual:
The list is still empty

In the network tab the following request is failing with 404:
POST http://v2ee.prod/admin/api/ezp/v2/views

No route found for "POST /admin/api/ezp/v2/views" (from "http://v2ee.prod/admin/page")