This is a quick one.
Multiselect in a UI designer is a pretty standard operation. If I want to change a property on a number of controls at once, I should be able to simply ctrl-click them (or command-click, or option-click, and so on) to select them all, and change the property.
Unfortunately Interface Builder doesn’t seem to support multiple selection on controls in different UITableViewCells. Attempting to do so always results in the first control being deselected.
However, there is a workaround, which is why this entry is really half ‘iOS Pain Points’, and half ‘iOS Quick Tips’. It turns out you can multiselect across table cels by command-clicking in the Document Outline window on the left.