I found the answer myself. Looks like this new version does not support these features anymore: http://www.adobe.com/ro/products/flash-builder/buying-guide.html.
The question rising here is what happens with this feature?
Will be available with a future update?
Will no longer be availalble in FlashBuilder, but in another Adobe Project?
Will never be available?
I belive this features are not important for advanced users... but I'm just learning this. I'm used to work in Flash. I write ActionScript, but I'm not familliar with the objects availlable in Flex, so the Component Panel and Design Mode is quite handy on this stage.
Plus, there is a real concern about the future of this technology, now beeing available HTML5. So, there is a question of oportunity investing time in learning things no longer supported. The most frustrating thing is not having an answer to this question. Even a "No" is better than "We don't know yet" <- the answer I received from online support.
The quick answer is, no there will never be design mode again.
Even for us "advanced" users who have been doing flex forever it is still a missed feature.
My solution has been to keep Flash Builder 4.6 installed side by side with 4.7. When I begin new projects I do my first screen designs in 4.6 in a general project I have for all UI developement. Once I settle on design layout and basic style I copy those into my 4.7 project and continue my development in code. I find it easier when initially doing design to be able to flip from code to design view even if I dont drag components onto the stage. In 4.7 the process is slower (and would be harder as you said if you dont know the components) because to view the design you need to build and look at it in the emulator/simulator.
As for is this a viable platform, I think it is although support is lacking. The Apache Flex project is doing their best and Adobe keeps pushing out Air updates, so all seems well. The problem is the tooling. There hasnt been an update to Flash Builder in forever and who knows when one is coming. I use it because I have a creative cloud account but I have contemplated ditching it for a subscription to FDT (http://fdt.powerflasher.com/). It is a more active project/product than FB at the moment, but I do a lot of mobile development and Im very comfortable in FB so its hard to make the change. Plus Im trading the entire Adobe software catalog for a single program.
Hope this helps.