The ability to lock not only objects but also topics.
Changing the geometry of smart objects can sometimes lead to ugly jumps of related floating topics or other nasty visual accidents. This cannot always be avoided and the consequences are so time consuming that they cannot be ignored. Particularly complex constructs, which continue to grow and often require radical redesign, can easily lead to such situations.
Hence my suggestion: Let us also lock individual topics or entire topic groups, or at least all topics at once. This would make it possible to reshape all types of objects without causing undesirable side effects.
This would be a bit like working with layers in any professional graphics software. Anyone who knows this will no longer want to work any other way.