According to the documentation of Qlik Catalog, instance installed as a single node lacks of the functionality of adding a field to existing entity. The button for adding the field is still displayed.
If the user does not enter the field list from the view fields button on the entity tab, but enters directly a fields tab - the button disappears, which might be confusing at first.
The idea is to work on the UX part - to hide the button when it is not possible to use it and to always show it when it is possible to do so.
