Ya, I'd like the add button to be set to `Infinity` already. Problem is, when the user reorders the items, we do a `Lookup.prototype.rearrange()`, which sets the index of each item based on its current position. By the time `onReorder()` is reached, the `grid:index` value of the add button would be, for example `5` when there are `4` dialogue states. Any new dialogue state would be appended after the add button, so we need to reset the add button's index to `Infinity` each reorder.

Maybe I should add a comment on this? I'm up for suggestions on a better way of doing this.