Could you explain where you are seeing this crash? I tried to break a transform node in an actor blueprint as well as an animation blueprint without crashing. Are you able to reproduce the crash in a new project? If so please detail the steps that cause the crash to occur. Additionally, if you are using the Master branch of GitHub (since you mentioned 4.11) you may want to try a more current version of the branch in case the issue has already been resolved.
I created a transform variable in my AnimGraph and set it up to match your screenshot without crashing. Again, if you’re using the GitHub master branch (4.11) it is possible that changes that have gone in could have fixed this already. If that is the case you should be able to download the latest version.
How are you setting up your anim blueprint? Using the third person template project I tried creating a new anim blueprint with the default UE4 skeleton. Inside the animBlueprint’s graph I created a transform variable and split it with a “Break” node then wired it into the Transform (Modify) Bone node. If you are using a different method to setup your blueprint please list the steps taken that cause the crash for you. Also, could you post the callstack and log files from the crash to provide additional information?