I prefer to work with open windows folders open so I don't have to navigate all over the place using the parts library flyout in solid edge. I find it easier and have worked this way for as long as I can remember. In an assembly, if I want to add a part I simply find it in my folder, then drag and drop it into the assembly and add relationships and move on. Starting last week this stopped working. It still works if I use the Parts Library, but doesn't work if I drag from windows explorer. When I drop it in, the cursor changes as if it is going to place it, but then it just stays like that with the little + sign. See video I just recorded below. Sorry about the aspect ratio I needed it to show more than one monitor so you could see everything.