I have a requirement to move from Kibana version 5 to 7 and as the layout of the kibana has completely changed there is a requirement to hire someone to be able to customise the look and feel. This requires someone with knowledge of the kibana layout. Im aware there is the ability to create an app that overrides the theme from reading more than from practical experiance. In our version 5 we simply modified the below, but this method does not work in version 7.
$KIBANA_HOME/src/ui/public/chrome/directives/global_nav/[login to view URL]
$KIBANA_HOME/src/ui/public/chrome/directives/global_nav/global_nav_link/[login to view URL]