Subactions in Unified Service Desk are actions within actions. They are useful if you want to tie actions to a certain action.
For example, let’s say every time a dashboard hosted control is loaded, you would like 2 other hosted controls loaded, which are web pages for Google.com and Bing.com.
You could create an action that loads the dashboard hosted control, and have another 2 actions that load the search pages. Or, you could bundle the loading of the search pages in with the action of loading the dashboard. That way, anywhere you call the loading of the dashboard, the other two actions will come with it, through sub-actions.
In our example, a dashboard loads on DesktopReady:
If we select the Action, on the right menu we can see Sub Action Calls:
We have an action that loads the Google page:
Now when USD loads, you will see the sub actions being called: