Unused models in drawings can only be deleted one-at-a-time from within the drawing and are only accessible from an old DOS-like menu. Unused models can accumulate from drawing revisions, and if a drawing is copied and views are edited. You may not even know you have unused models that are taking up memory and time. Modelcheck can be used to strip unused models from a drawing, but that's another step that shouldn't be necessary. Suggestion: Cleanup the drawing model selection menu and add the ability to select multiple models to delete and/or the ability to delete all the unused models at once.