Not sure if i understand your question entirely. But if you mean that you want to perform an action in AppGyver in reaction to a response from a Bubble workflow API then that is very easy to do and there are some examples in the tutorial on the Login button logic.
You simply call your Bubble Workflow API endpoint using a Create record (remember that all Bubble workflow API endpoints are POST). Then in the output of the Create record action you add the action you want to perform, e.g. Go to another page, download a file etc.
For example in the tutorial the logic for the Login button is as shown below. After the Create record (1) action which is a call to the login workflow api we perform some steps, i.e. Set app variable (2), Set item to storage (3) and Dismiss initial view (4).
So you can perform any actions after calling the workflow api endpoint. You can also perform different actions if the call to the workflow endpoint failed. In the example above if the login workflow api fails (second output of the Create record) we perform a different set of actions - in this case Hide spinner and show a Toast.
Note that AppGyver doesn’t have a webhook mechanism that will allow your app to sit there waiting to react in response to some event that occurred in your backend. So if you want something to happen automatically without a user’s action, then you will have to pool your backend e.g. do a Create record every X seconds using the Global Canvas page and perform the necessary action accordingly. If the action is to be initiated by the user then you simply call the workflow api and add the actions like I’ve done in the login button logic above.
Hope this makes sense.