It may surprise you to know that although 2018 is still at beta 1 (check it out here) we are already researching possible functionality for subsequent releases; a vital part of this research is feedback from you, our users!
I'm interested in hearing whether you need to know more information about the available degrees of freedom (DoF) for under defined components, and how we could best present that information to you.
Not all cases are straightforward.... take the robot arm shown below: notice most of the components are under defined because they are free to move relative to the assembly origin - as per the design of the robot arm, therefore they have multiple DoF relative to the assembly. Conversely, they are correctly and "fully" mated to their adjacent components, meaning they have zero or one DoF relative to the component to which they are mated. So depending on which context you use, the tip of the arm could be reported to have a variety of different numbers of DoF.
For those of you interested in sharing feedback on this please could you message me directly in the forum and provide your email address - I'll send you an invite to a very short survey - it should only take a few minutes. Click on my username or profile picture to access the Message function.
Note that the presence of this forum discussion doesn't guarantee that we'll be offering any such functionality in the future - this is purely research!