Classes which are connected to other classes via an aggregation/composition using a UML qualifier have by default multiplicity of 0..* ("Note that in this particular case ―LowerBound‖ is hardcoded to '0'"). Hence, they are optional but there is noe way to deselct such classes in the tool, i.e. they are handled by the tool like mandatory classes.
You are right.
Personally, I found it a little odd that a qualifier is alwas 0 to *. But, I know that we have discussed and decided earlier so I hope we are doing the right thing.
Added check when loading tree if relation has a qualifier then possible to deselect child.
Included in build 3902 released 2010-09-07