QML's TabView (v.5.5) does not support close button for closing tabs. It is not as easy to add as mouse events can be passed only if it is a style.
I put my implementation, with many qt bug workarounds, into a reusable example:
http://www.qml-object-library.com/li...-closable-tabs
Or, also on the same subject: https://forum.qt.io/topic/37649/solv...n-tabview-tabs