1) is there a way to refresh an App from another one? From Qlik Branch I've found an Extension called Reload button, but I'm only able to refresh the App containing this button...
2) how can I setup inside QMC triggers to start the refresh of an App upon the run/reload of a specific qvf?
You can set a trigger based on a time interval or based on the completion of another task.
So, for your scenario, whenever the task that rebuilds the qvf completes, you can trigger another task.
First create 2 reload tasks,
Reload Task 1 - reloads your initial qvf.
Reload Task 2 - reloads your dependent qvf
Add a trigger to Reload Task 1:
Create a new event task event trigger:
This will create a linked task. When your qvf reload job (Reload Task 1) completes successfully it will automatically start the reload of the dependent task (Reload Task 2).