I have yet to figure out how to put a link on my favorites home screen to a frequently used spreadsheet. Any help would save the few hairs still left on my head...
The only solution that I have was to take the Files Folder Icon from the Applications Folder and add that to your Favourites tab, because when you open it, it gives the option to have files set as faviourite, so they appear right away and you don't have to go fishing for them.
When the file is highlighted and I press the "berry" button there is no choice for favorite. At the bottom of the screen there is a star to favorite but it only makes it a favorite within the file folder. I have also tried to copy/cut paste to mainscreen but paste is not an option on that screen.