This question has been answered by sottwell. See the first response.
There are a number of permissions that are needed to access the Manager at all.
Try assigning your user to a group with the "Editor" permission. If all you want the editor to be able to edit is a resource's TV, then you'll need to use Form Customization to hide everything else for users in this group.
To log in, a user's User Group needs a Context Access ACL entry for the 'mgr' context. To see resources in the tree, they also need one for the 'web' context.

1. Create new User Group:
Name - Editors
Contexts: web,mgr
Manager Policy: Content Editor
2. Right-click on the new Editors group and choose Update Group.
Open the Permissions tab.
Context Access: Access Policy for web and mgr - Content Editor
3. Create new User
Access Permissions:
User Group - Editors
Role - Super User
Here's a nice tutorial on customizing the resource editing forms using Form Customization. You can use this to move fields around, hide fields, and other customization. http://www.cmstricks.com/blog/2012/08/27/integrating-a-template-into-modx-part-5/
[ed. note: yawnuser last edited this post 11 years, 4 months ago.]