I used to be able to do this but now, I'm not sure what happened. I used to
have one excel up and I was able to toggle between two workbooks (by
minimizing whichever one I didn't need) and copy cells/formulas/data onto the
other workbook.

Now I have to open two excel workbooks at the same time, but them side by
side in order to copy/paste the data.

Did I mistakenly change a setting on my computer?