Currently you can look at the list of proposals by progress, but if you want to see the ones that are only in the definition stage you have to hunt for them. It would be nice if this could be broken out somehow.
If you are viewing by progress, you shouldn't have to hunt for them. They're all grouped together starting on the second page. View by 50 proposals at a time and it is one click.
You can also select a 'category' (on the left) to make the list shorter.
I don't imagine the developer would add another entire tab or a button to break down that list even further.