Switching to Model Workspace
When working in a Sheet, the ModelMode command lets you toggle from Sheet workspace to Model workspace.
You can draw or edit entities in Viewports although your working space is a layout Sheet.
If you have multiple tiled views on a Sheet, you activate a specific one by clicking it.
To switch back to Sheet workspace, use the SheetMode command.
You cannot use the ModelMode command in the Model tab.
Access
Command: ModelMode