We've never needed aligning things like that regularly, so we never made a shortcut for it. I think we've made something like that once, but since we always have a controller script sitting on the base, we simply positioned it in the center using that...
If you want an automated way to do this, you can place invisible/empty uiItems on either side, set to expand to fill, i.e. 2 proportional ones, and one fixed size thing in the middle. Its not ideal but it does work.