I know that the Viewer Pane can be positioned in a right-side column within the lister (sharing that column with the Metadata Pane if present), and I know I can reposition the Viewer Pane to the bottom of the lister as well. Here it is on the right:
I work with a lot of PPT slide decks, and would ideally like that Viewer Pane to sit directly below the Folder Tree - I'm willing to give up some of that vertical Folder Tree space if I can get the Viewer Pane down into that corner, directly below the Folder Tree (which would also give me back a lot of unused space in the right column in the first screenshot above).
Something like this mockup, perhaps:
Not doable today, I'm pretty sure, but perhaps in the future that Viewer Pane could be dragged/dropped/resized/floated to locations other than the right/bottom choices we have today?
As in the mockup, if the Viewer Pane was dragged to another part of the lister (such as the left-hand column below the Folder Tree), it would "share" that space and I could drag the separator up/down between the two panes to resize to my liking.