[MatthewS]

Is there a way to lock the aspect of an object so that it won't change even if the group its in gets resized?

It would be helpful when dealing with pull-down form fields, since I want to resize the text field width without having to fix the arrow.

Visio calls it protection
Axure doesn't do it.

[andyshan]

I don't think this is currently possible in Omnigraffle, and I believe (unlike in Visio) this is a behaviour which isn't widely standardised or required.

You could ungroup and regroup the items you want to resize instead, then regroup the new set with the one object you didn't want to resize. A bit of a workaround.