How to make a window like this

If you are using a Cocoa-AppleScript template, you have some work to do. Since the Interface Editor isn't available, you are going to have to do everything by hand. One way I've found that makes it a little easier is to create the UI in the Interface Editor, then look at the raw nib/xib file to see what the numbers are.

From the Interface Editor in an AppleScriptObjC Xcode project, there is a Window and Drawer object that you can drag from the library. This has a Drawer Content View that you can put your other objects in. In your screenshot the view has a label, a text field, a popup button, and an NSOutlineView.

The window has the makeKeyAndOrderFront method, but the drawer view does not, since it is attached to the window - see the NSDrawer Class Reference.

1) You can create whatever views you want, then use NSDrawer's setContentView: method to set the desired view before opening the drawer.

2) You can try to convert AppleScript Studio, since the various predefined handlers are basically wrappers around the equivalent Cocoa methods, but your best bet would be to use the Objective-C documentation - Outline View Programming Topics, for example. You will need to learn to read the Objective-C method declarations (and know your way around Cocoa), but the conversion to AppleScriptObjC is fairly easy.

A drawer can't be larger than its parent window - see Drawer Programming Topics.