I just picked a bunch of surfaces and added a hydrostatic load only to realize I had missed one surface. Now my choices are to a) delete the load and try again being careful to pick all the surfaces or b) pick the surface I missed and add another hydrostatic load which is exactly like the first one.
It would be much nicer to simply add another surface to the existing load. I've never understood why it doesn't work this way but after making this mistake for the millionth time I decided to submit it as an idea. This, of course, wouldn't just apply to surfaces. Any load and entity that makes sense should work this way.