You mean like a button?
I am using the following Fireworks extension:
On STEP 1 in that post you can define a Group Height and Width to a group of images.
When I do that the images seem the same but when I click one it actually has the new size.
I was wondering how is that done?
What about grouping it with a transparent rectangle (a rectangle with no fill) that's 30x30?
What you are describing is having the bounds larger than the actual object. What are you trying to accomplish by doing that? Are you hoping the larger bounds will snap to guides/grid/objects?
I agree the only obvious way would be to group a transparent object. There's certainly no built in way to "add margin" in the way you describe. A script could be made fairly easily to automate the suggested workaround.