You can create an initial node by selecting it from the tool palette.
If you’d like to create only one initial node per Activity diagram, go to [Tools] – [System Properties] – [UML] and enable the option below:
You can create an action just by double-clicking on a diagram or any other ways that are described in the Diagram Editor page.
Also, you can insert an Action by placing a new or existing action directly on the transition line.
By default, Actions aren’t on the Structure Tree. So in order to show them, you need to change the setting in the System properties from [Tools] – [System Properties] – [Project View].