I added a release to a user story map, and moved around my features into the columns. I a clumsy attempt to add in an existing release, I clicked the floating "add release" button, and it moved all of my features to the new, undefined release. no bueno.
Thanks for the idea!
We have updated the way the Add release button works, which should solve the issue you noted in this idea.
Now, only the Add release button itself will create a release versus clicking anywhere along the release line. This will make the act of adding a new release on the user story map more purposeful and reduce accidental creation of releases.