pjax is the tool to load and update html , this deactivate the default behaviour (unload html, reload html).

Hey again. I've managed to progress a lot further. However, by throwing out most things, I've apparently broken the links at the top of the surveys ("Continue later", "Abort and delete" etc). I've figured that they are most likely missing required onclick event handlers. activateActionLink() in survey.js should theoretically take care of it, but somehow doesn't do the job as expected. I still have the subviews/header/head.twig included, which calls:

I assume I must have deleted/edited some part of the layout_global.twig that was required for the above line to work. If anyone could point me into the right direction, that would help me a lot. Cheers!