Today's 'duh' moment: Outlook
After using Outlook for so many years, I thought I'd figured out all of the shortcuts and tricks I needed for the way I work, but somehow a little feature crept in without my notice that I discovered by accident today.
I use a lot of folders to organize my Inbox. Some emails go to the correct folder by Rules, and the rest I drag and drop. Today, as I moved my mouse, I discovered that the "Move to Folder" icon had listed all of the folders I used recently - I swear I've never seen that icon or its menu before! And so, my duh moment: fewer therbligs to mouse-over and click a folder name to move the selected email than my previous method of dragging the email down through the tree.
12 Oct: edited to change source of screenshot...my other method just wouldn't work consistently