See here.

https://github.com/StateSmith/StateSmith/wiki/draw.io:-tips

This page details some of the things that the plugin makes easier.

Either double click on the group, or use the enter group button. This can make navigating easier.

Hold either CTRL or SHIFT and select multiple states. Then use the Group command. The Group command is available via CTRL+G, from the right click context menu, or the top tool bar under Arrange > Group.

You can either drag shapes in from the sidebar or just click on them.

Note how the plugin automatically renames the state to help save you a bit of typing. Auto renaming currently doesn't support new style of declaring state machines without children nested inside.

There' a number of other things that the plugin makes easier.