Astah has keyboard shortcuts to zoom in/out diagrams which is helpful enough but if you master a [Map View], diagramming will be much easier especially when you are working on a large diagram.
■ What is [Map View]?
[Map View] is this mini map shown in the left-middle of Astah.
■ What does this [Map View] do?
This Map View shows a whole diagram that is currently opened in the Diagram Editor. The yellow rectangle is an area that is appearing on the Diagram Editor. So by moving and resizing this yellow rectangle, you can change what to show on the Diagram Editor.
Let’s drag the yellow rectangle. Diagram area will move along with it.
You can create a yellow rectangle by right-dragging to crop the diagram to show on the Diagram Editor – anywhere in any size.
■ Hide Map View
Since version 7.1, Map View has its own view. But if you are not going to use it much often or you want more of the [property view], you can disable this View. To do so, go to [Tools] – [System Properties] – [Project View] and disable this option below. (Click [Apply] – [OK])
Reboot Astah, then the [Map View] will be included in the top-left pane under [Tab]