On QT5 Ubuntu 16.04.1, the delete key no longer works and so I have to use edit delete to take out unwanted sections. Is this intended, it slows down editing a lot?
This could be related to QT appmenu. See if this helps:
Remove appmenu-qt5. Install/ leave installed the appmenu-qt:amd64
see here for more info:Shortcut ubuntu 16.4.1 QT5] Ctrl x (http://avidemux.org/smif/index.php/topic,16954.msg75843.html#msg75843)
Yes, removing appmenu-qt5 has restored the function of the delete key as you suggest. What are the implications of this?
The SABDFL once decided to integrate menus of all applications into the top bar of Ubuntu's desktop shell to spare a few px of the precious vertical screen estate (back then, netbooks with 1024x600 displays were the future). It never worked really well. appmenu-qt5 implemented this feature for cooperating applications which used the qt5 toolkit.
Without appmenu-qt5, the menus for these applications will be shown in their menu bars instead of in Unity's top bar. As for all other qt5 applications, they won't suffer from appmenu-qt5 related issues like this one anymore.