In AutoCAD Mechanical toolset, two main workflows use formats and layouts that are supported in mechanical structure:
In AutoCAD Mechanical toolset, paper space is used for creating a finished layout for printing or plotting. You do design work in model space when you want to annotate geometry you create annotation views in paper space.
In paper space, the mechanical browser has one tab. The Drawing tab is synchronized with the Model/Layout paper space selection, and lists a Layout node for each active layout in the file. Inactive layouts are not selectable.