On several occasions, Domino Designer falls short when it comes to developing XPages. On those occasions I try to dive into the XPages API. I used to create a computed field with the value of typeof getComponent( 'component-id' ). This gave me the class name of the object. Then I declared a variable with the type of the class. This gave me the methods available for the component type. E.g.
var field:com.ibm.xsp.component.xp.XspInputText = new com.ibm.xsp..
It started with a simple field that you put a class name into. This gave you the properties and methods of the class.
Then I added the functionality to type the name of a global object (e.g. facesContext), and it printed the properties/methods of that object.
Then, while writing/preparing this blog post, I remembered my client side getClientId/getComponent. After a little bit of copy/paste/modify, I ended up with a custom control that lets you select any control (including event handlers/etc) on the page from a combobox (just add the custom control to the XPage you're developing), and get the methods and properties of the corresponding class in the XPages API.
A couple of screen captures (animated gif):
>> Download Demoapp with custom control (28K zip)
In theory, the custom control lets you post commands to the server, so remember to modify the ACL after you download!
Share and enjoy!