On the page [https://support.microsoft.com/en-us/office/work-with-packages-in-uml-models-b4b5fb18-1879-44e1-904c-023318cb8046 are instructions on adding an add-in that seems to do what I want to do: When a package is added, I can click on the package and that will take me to a new Page where that page is added to the package and I can draw a class diagram or whatever. (It's usually a class diagram.) The instructions on the references help page say the following, but I can't see how to make that work in Visio 2019 Pro Desktop version. (These instructions are for earlier versions. Can't find anything later.)
Create a new package from a diagram
- In the tree view, double-click the icon for the diagram you want to add the package to.
The drawing page for the diagram appears.
- From UML Static Structure, UML Use Case, UML Component, or UML Deployment, drag a package shape onto the drawing page.
An icon representing the package is added to the tree view.
Create a new diagram from a package
To automatically create a new diagram each time you add a new package to your model, on the UML menu click Options, and then, on the UML Add-In tab, select Create a diagram page when a package or subsystem shape is added to a document.
To create a new diagram if this option is not selected, right-click the new Package shape and click Diagrams, and then click New. Type a name for the diagram and select a diagram type, and then click OK.
Add elements to a package
In the tree view, right-click the package you want to add elements to, click New, and then choose the type of element you want to add.
An icon for the element is added to the tree view.
Represent package contents in a diagram
- In the tree view, right-click the icon for the package with contents you want to represent, and then choose the type of diagram you want to include in the package.
The appropriate stencil and a blank drawing page appear. A watermark with the name of the diagram type appears on the workspace.
- Drag shapes representing the elements you want to include in the package onto the drawing page.
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