It seems like that for the last several years I've stumbled over new stuff that didn't make it to the "What's New" documents (see SW2016 Fixes That Didn't Make the "What's New" Document and SW2017 Enhancement That Didn't Make the "What's New" Document). It looks like I found one this year too. When working in a weldment Part and using the Structural Member function, pre-selecting the sketch line or lines from the graphics area before activating the command works. It never (as far as I know) did before. I realize this saves one click at most, and for sketches with more than one line segment it won't save any, but I still kind of like it. I'd love to have it also work when selecting the sketch from the tree, but maybe next year?