Yes, but I am afraid I cannot make it happen in the coming release, and this is the reason why I intended to keep these shortcuts as secrete 
I’m wondering whether it would be possible to make the middle mouse button (i.e. pressing down the mouse wheel) move the Preview image around in the same way the middle mouse button moves around the canvas window?
I would find it very helpful, and it would also make the UI consitent between the Canvas and Preview windows.
Yes. There are some other points:
- instead of top-left conner, zoom should be from the center of the current view of preview, or the position of the mouse pointer placed
- preview window should also be able to grab the canvas size for the first time user calls it
I am going to cleanup the current code, merge the Preview Options Window into preview window itself before start to implement above things. Not sure if I can start it quickly, sorry .
I found a bug in the preview options, filed a report here: https://sourceforge.net/tracker/?func=detail&aid=3524682&group_id=144022&atid=757416.
In short, negative start frames mess up the range.
thanks for report it, and after more than 0.5 hours code reading, it is fixed in my local repo. As additional bonus, now I know more about the code of Preview Option, it seems I am ready to merge Preview Option dialog to the preview window 
Fantastic! Thanks! 
Another thing that would make preview window yet a little better is to keep it above all other panels.
At least in my systems it has the same stack order as the canvas (or just above it) so it goes on top of the toolbox but behind every other panel. Thus making it impossible to make it larger or fullscreen without it beeing obfuscated by other windows.
already in my git repo and the size of preview window now inherits its canvas size too.
What format do you prefer?
- Previewing : Canvas Name
- Canvas Name (Preview)
To be honest, window and dialog titles that identify particular canvases need to be thought about across the whole program. We need a uniform way to identify them.
If you look at the Properties Window for a canvas the hyphen-minus signs are used. In the canvas window colons and brackets are used. In the Properties Window the Canvas name is used, in the canvas window the Canvas name and the file name is used. The Properties Window never uses the word “Root” but the canvas window does - so it gets a bit complicated!
So as you’re working on the UI for the whole program it would be better to leave that choice up to you.
Good point, I added this to the "the problems we want to solve "Before final decision be made, the temp solution I prefer is “Preview - Canvas Name”.