I know this is older, but I have my own question to this topic. I don't have the mouse object in the ''objects with expressions'' and downloaded another project with the mouse inside. I tried to drag'n'drop it to my project from ''projects'' on the right side, but it doesn't function. So how do I add it to my own project?
Edit: I see there is the mouse already on other 'new' projects. I haven't done much, so I can improvise and take my own saved objects just to a new project, where the mouse already exists, but it would be great if there still is another way to get the mouse to a project...