I find myself going to the same project workboards again and again. I have a list of flagged items (Maniphest tasks and Phriction documents) on my home Dashboard to make them really easy to access. I wanted to make the workboards similarly easy to access (at the moment, I look through my assigned tasks to find a project icon to click, or go the long way through the Projects app). I noticed when I set up the flagged items panel on the dashboard that 'Projects' could be chosen as a filter for the flags, so I'm guessing the support is there architecturally, but it just needs a UI to create the flags. Would be really nice to have that feature.
Ah. Looks like I just needed to upgrade as this change was made in the last month or so (I last upgraded late Feb). Didn't see this change mentioned in the changelog, or a task for it, so assumed it still wasn't possible. What you have implemented is perfect for us. Sorry for the noise.