You do not have to migrate any script at all. All you need is to copy the file across to C:\Users\<User Name>\Documents\Qlik\Sense\Apps and then open Qliksense. You will find that the QVW is shown up in the hub. Just open it, reload the document and the QVW is converted into QVF. As simple as that.
You need to build the UI and can role it across. It has taken only one week for us to role out all the existing Dashboards in Qlikview to Qliksense.
Hope this helps.
Every thing is the same with the external script inclusion.
The external script which you had in qlikview might have been embedded like this:
You can achieve the same in Qliksense using :
The only difference being the URL replaced with a data connection.
Hope this helps!