I have to stand by my original suggestions.
See 12.3.1 and note extactly what it says about pointing devices with sidebars. It also covers placement. I think you will see that what I said reflects that. You might want to consider the purpose of that pointing device in print and how it serves the print reader. The arrow had not meaning to the braille reader. It is the PLACEMENT that has meaning and the arrow is used by the transcriber to determine placement.
As for inserting a box inside a box, I also stand by what I said. The sighted reader can see whether one box is actually inside another in print. The braille reader cannot. I strongly disagree with informing the braille reader that a box is printed inside another box when in fact it is not actually printed that way.