I'm working on a multipage table created by someone else, and randomly scattered through the table are these mysterious boxes or sub-cells that show up when I click on some of the text items.

The boxes are sized to the text and so don't fill the cell, and display a grey, three-dot tab on the left when clicked. When unclicked, they are invisible, although the text within them displays normally.

I suppose these are some sort of a feature rather than a bug, but I have never seen them before and I've been using Word since Version 1.0.

The problem is that they're a pain in the ass to manage and also complicate the process of formatting the text (especially since some of the text in a given cell is inside the box and some is not). Perhaps if I knew what they were supposed to do, I could take advantage of them, but I'd be happy just knowing how to get rid of them.