Previously, when you moved an issue to an assignee or milestone that wasn't displayed on screen, the issue would disappear into the ether.
Now, when you move it to an assignee or milestone that's off screen, we'll display the assignee / milestone and move the issue to it:
One exception to this occurs when when you're filtering by criteria that would exclude the new assignee / milestone from being displayed on-screen.
For example, if you're filtering to only show issues in the Q2 milestone, and move an issue to Q3, we won't bring up the Q3 milestone. Instead, we display a message letting you know the issue has been moved:
Thanks to @ezrabg for the suggestion!