Yes. You can add multiple files to your Content Library at the same time.
The easiest way to do this is to drag and drop files from your desktop/shared drive directly into the Content Library area. They will upload in the background and you'll then be asked by Slidebank where those files should live.
If you want to upload multiple files to the same location, either drop them into the same folder in the library, or use the 'Upload Files' button in the nav bar, which will guide you through folder selection as well as metadata tagging and file access.
For more information on ways to upload content, see here.