Need to try and get a video picture running in my head about this first rapidred...
First and foremost, I'm not sure if a USB3 stick will work... I used a USB2... Then you said you formatted the stick... Did you do that in the Chromebook, or was it done otherwise??? Let's move on a bit...
OK ~ you then started by saying: I 'cleared' that by clicking on small up arrow on right end of menu box.
Personally, I used the small 'X' in the top right hand corner, as in windows practice... Is your arrow the equivalent to the 'X' ???
You then said ~ a little further down: I selected download and green down arrow indicated file had downloaded. (That was correct) Then you said: File shown in bottom left. However I could not select the USB drive and could not find save. The USB drive no longer visible and I couldn't bring it up.
In my case, the main 'file menu' opened, allowing me to highlight the USB ticket, and click on save, at the bottom of the menu file... That's where your usage, seems to differ from mine ~ for starters...
If you'd placed the 'file ADD', down on the shelf before you started (if that was possible) you could have opened the file envelope, highlighted USB and saved ~ as I did on mine, then opened the file again, to see that the picture had gone onto the USB stick... Hope that makes sense...
That seems to be the major difference, between what I did and what you did... If you've the patience, would you try to replicate my process, before going any further, so that we only take one step at a time...
Like you, I've been at this for more than a decade, using windows (all self taught) and at times, I've found that it's only been sheer determination, that brought success to any project...
Maybe you'd let me know if you want to proceed, or give it all a miss...
Regards...
Robbie D....