How to update DocProperty fields with Word js

I am developing Office 2016 Addin using Word js 1.3. Addin allows you to define custom properties and store their value.

I would like to add a button in the UI of my Addin that updates all fields using DocProperty (see Figure 1) in the document that uses custom properties added by the user. Basically the button should update the fields (see Fig. 2).

I mean the following things:

I am unable to wrap fields in ContentControls and then update them. The documents are preconfigured with some custom properties and their content cannot be changed.