How do I close a "Document Pane"

I have just recently installed R2025a and I am fairly new to the new desktop environment in general. I find on occasion, as I massage my desktop layout, that an empty pane with a '+' icon appears (see below). It seems to serve no function but to open blank editor documents, which I don't really need - the Editor itself does that just fine. Importantly also, there appears to be no way of closing it, though it can be dragged around the desktop to different locations. Is there a broader purpose and functionality to these document-launcher panes that I am not seeing? And regardless, how do you close them?

Answer 1

[Matt J]

So, I have figured out how to get rid of it, but I'm still curious why it is needed...

It only appears when panel icons are placed on the right and left bars simultaneously, and the bottom bar is left empty. For the figure above, I have the Files panel anchored to the left sidebar and the Command Window icon anchored to the right side bar, but nothing on the bottom bar. Apparently, when the right and left sidebars are both used, only a 3-column layout is possible, and the "Documents Pane" is used as a place holder for the empty middle column.