Though you can make terminal splits really easily, closing a terminal split often results in really unfortunate terminal arrangements and you will want to rearrange them. There is no way to rearrange the splits right now that I can see.

It would be nice if users could rearrange terminal splits via mouse drag-and-drop. You can try out Tilix (another terminal emulator) to see an example of what would be ideal behavior (just click and drag on each terminal split to rearrange them).