While I was drafting this, both you and Ben posted some good comments. I'll go ahead and complete my post in hopes of shedding some light for others who may be wondering.
The Word linking icon is new to RoboHelp with version 8 and many folks are still getting the hang of it, so I'm glad you asked the question. As you have discovered, that green icon means that the Word document is linked and is up to date at this point.
One thing that will not be obvious unless you "look under the hood" in the Windows Explorer is that the icon actually represents a "real" subfolder that has been created automatically on your hard drive within the project folder structure.
That new folder is automatically created bearing the same name as the Word document. When you right-click to "generate" the .htm content, this is the folder that will contain that content (along with any graphics or .css files as a result of the Word conversion).
So moving along, if you use the "Automatically create TOC" feature to create your table of contents, the Word-created folder will be treated as a "Book" with whatever topics shown inside. (As you have discovered, you can workaround this manually with drag and drop.)
Within the Project Manager pod, the reason you don't have any text showing (or a topic displaying in the Design Editor), is that the Word-folder is not a topic and thus has no text. It is simply a container for the topics inside.
Now, if you don't like the idea of the Folder showing up as a Book in your TOC (or as an organizer as you put it,) you can simply move the Topic(s) inside the book to where you like and delete the "Book" icon in the TOC editor.
Or, as Ben aptly suggests, you can also edit the properties of a book to have it link to a topic of your choice by the method he describes in his post.
Hope this helps.
Thanks,
john