Sharing an actual Q&A between Astah Support and customer regarding Sequence diagrams.
[Message Parameter Type Visibility (initial setting)] does not apply to Create Messages.
In Astah, you can adjust lengths of lifelines and ExecutionSpecifications in UML Sequence diagram easily. You no longer adjust those lengths one by one. You can adjust them all once before you export diagrams to image files or print!
When you scroll sequence diagram or activity diagram, it should show the names of the lifelines/partitions at the top of the diagram when they scrolled out of view, however it will stop showing after a particular operation.
How to remove the message numbers in Sequence diagram.