Don't know why it's not in there but would be good to have. The only way to do this is to click Zoom tool and then click the little "Fill Screen" button at the top. Can you add it to the Ketboard Shortcut list?
There are not enough shortcuts to go around for all the tools, so we try to limit ourselves to only the most popular ones. That said, you can customize your own shortcuts by going to Edit > Keyboard shortcuts and adding a shortcut to Fill Screen yourself.
Hey there David, sorry if I wasn't clear enough. My request is to have it added as an entry under "Edit » Keyboard Shortcuts..." because it isn't not listed there at all so right now there's no way to make a shortcut.
I have only found "Fill Screen" as an option when the Zoom Tool is active. Selecting the Zoom Tool, then clicking a little button in the Options Bar.
Unless there is some unknown way to manually create a shortcut entry from scratch, I don't see anyway possible to make it a shortcut.
Thanks again David, let me know if I'm right or if I've been missing something.
Now that I better understand your question, yes, unfortunately as Fill Screen is not a menu command and there's no equivalent menu item, you cannot set a keyboard shortcut for it.
For what it's worth, I have used your comment to create a feature request and spoken to some folks about it. Hopefully, this will get implemented.
I'll add my vote to this. One thing to consider is having it work in Full Screen mode to where the image works like Fit Width in Acrobat. I'm thinking the collapsed panels and Toolbox might stop that short.
This may not be the answer for everyone, but if for wallpaper purposes I need an image to fill screen, I open it in Adobe Acrobat by selecting "All Files" cmd/ctrl L for full screen, cmd/ctrl 2 for Fit width. then scroll up and down to frame the image exactly where I want and take a full screen shot (cmd + shift + 3 on the Mac).
This may not be exactly what you want but it works, this will zoom the active document to 100%, filling the screen. Save it with a .jsx extension and add it to Photoshop scripts, then call it from an action that you assign a key command too.
The Feature Request is still open. There are a LOT of improvements in the pipe. User stories explaining why this change is important are very helpful in prioritizing such improvements.