When updating a source model, on the dialog which shows you the differences between the original and updated model (new/old/unchanged).
By default all the items are checked, meaning the source model will be updated to only what has been selected in the previous screen.
Most of the time we want to add tables to our source model. This means we need to unselect every item in the differences dialog except the ones we just selected.
There's no deselect all button, which we would like, so we don't have to deselect every checkbox one by one (especially when we have hundreds of tables in a model).
These checkbox items are the children of a checkbox for the schema, so typically in a UI like this you would expect unselecting the parent checkbox to unselect all its children also. This doesn't happen.