Why should SketchUp not disallow its customers to reuse their own files and refuse them all their rights and needs? 
As in SketchUp Pro, you find the file functions in the top left menu (which just looks a bit different). As a customer you probably have already a Trimble account although even free users can create one for free.
I remember at one time I could open local files without logging in to Trimble Connect. I am also wondering why you can find under the “open” icon (or the “folder” icon) the functions to insert skp and image files, but not to open another skp file instead of the current one.
