This is a very good idea. I use spreadsheets for other stuff, so I might for this game as well.
It also depends how early on we unlock the Museum to donate fish and bugs to as well. If it takes a few days, then I might go ahead and log everything I've caught but not donated in a spreadsheet if there is not an in-game feature that tells you. I usually donate creatures the first time I catch them, but I'm not going to wait to make bells if it takes awhile for the museum.
It also depends how early on we unlock the Museum to donate fish and bugs to as well. If it takes a few days, then I might go ahead and log everything I've caught but not donated in a spreadsheet if there is not an in-game feature that tells you. I usually donate creatures the first time I catch them, but I'm not going to wait to make bells if it takes awhile for the museum.