How do you make UML class diagrams in Freeform?

I am looking for suggestions on creating UML class diagrams with Freeform. I am familiar with creating them on diagrams.net and Lucidchart.

In Freeform, I don't see a way to add a cell that provides sections for class name, attributes, and functions. The only way I've found so far is to use the pen tool to sketch such a cell, but the disconnected dividers I draw and text that I insert doesn't drag with the rest of the cell.

I'm not sure if I can anchor elements to each other in order to create my own shapes—conversely, it can be tricky to group-select several elements, like if I had separate elements in close proximity.

Have I missed something, or do you have any tricks for using Freeform in this way?