In the render view, the "Render fir Content Spec" drop down menu would be more useful if it contained a product name as well as the book name. I can't get a screenshot but for a topic I am currently looking at (ID 8849), the list contains six "Administration and Configuration Guide" items. This information would make more sense with a product name since information that is usually included in one type of guide (Admin Guide) would likely be in the same type of guide for other products.
For context, I use this drop down menu to see whether the topic is used in any other product's documentation before thinking about changes.
For your specific case you should probably be using the "Content Specs" tab, as that was what it was designed for.
As for the RFE, this is more than likely going to cause the dropdown to contain too much data to the point where you'd need a 1920x1080 displays to be able to read the additional information anyways. As such we possibly need a way to group the Content Specs in the list by product instead, or maybe have another dropdown where you select the product first. Anyways we'll need to look into this more closely when we take a look at implementing this RFE.
As an additional note, as to why this shouldn't be used for checking if the topic is used by other product's documentation, is that the list only shows content specs that have entities or conditions defined. Any other content specs are all grouped under the "DEFAULT" option.
I ended up requiring having to do this anyway for BZ#1037269.
Added in 1.4-SNAPSHOT build 201402151749
The content spec list is now grouped together into product/version to help identify what content spec you are rendering the topic for. The groups are also sorted alphabetically to make it easier to find your topics.
Note: This version is currently deployed on the development/test server.