Ex: I create a button that consists of a rectangle with the text "submit" centered in it. No matter how wide or tall I make the rectangle, I want "submit" to remain centered horizontally and vertically within it.

Sketch allows this via "pinning". I can set a parent object-- in this case, the rectangle-- and tell a child object---in this case, the text-- to maintain a certain distance from the top, left, right, and/or bottom of the parent object, or to remain centered to the object at all times, regardless of how the parent is scaled.

In addition, multiple objects can be pinned to the same parent-- for example, if the button said "submit" followed by a checkmark icon, I could tell "submit" to maintain X distance from the left edge of the parent, and the icon to maintain Y distance from the right edge of the parent.

This would be a HUGE time saver for those of us who do UI work in Illustrator. I'm sure it would be a lot of work to implement, but if doing so is at all feasible its inclusion would be amazing.

Thanks!