Whenever a projected geometry curve or point is broken, you have to go hunting through the sketch to find it. This can be a huge pain, especially if the sketch is large or if the broken geometry is covered by something else. It would be so much easier if there were just an option to delete all broken references. After that, it would be easy to just find where the sketch is no longer fully constrained and make new projections as necessary. The user is only going to delete the broken geometry anyways; there's no reason to force them to try to find a needle in a haystack in order to do that.
Alternatively, if you could show projected geometry in the tree so that the user can just click on the broken geometry and click "show in window" or right-click >> delete it, that would be even better, but maybe harder to implement.
