Thank you for posting to our Ideas & Suggestions page. I can see that your product idea has been received and logged internally as CR-214962.
I'm not sure if you've received this already, but our Customer Success Managers have developed this app that hopefully will ease the pain of filtering by project: https://app2.clarizen.com/Clarizen/View/Default.aspx?id=42eea74d-55ad-40ec-a857-b0b0b49747c8&type=Published+Application&ver=v6
This app places a button in your work plan called "Filter by this project", which removes a few clicks needed to filter by a specific project. Please see attached for a screenshot of what this app would look like in action.
Please let us know if there is anything else we can do in the meantime.