Linking to dependants in other projects?

I have a recurring issues of projects waiting on other projects. Like I find out we can't start design on project A until project B gets approved, etc. And then I go to project A a week later and I'm staring at it trying to figure out why we haven't started yet. So I ask again and have the same conversation...

How do other project manager's reflect this type of information? I've started just commenting on projects/tasks with "update:" so that I can see what's happening at a glance without having to guess. But I feel this can be improved. 

Thanks in advance!