This is my code:
<move element="navigation.sections" destination="page.header" />
But the navigation bar disappears then. Whats wrong here?
Solution was to use
header.container. Found it via console:
grep -rl "navigation.sections" * to find out where this gets injected, because its close to the desired destination.
nano vendor/magento/module-theme/view/frontend/layout/default.xml to find the name of the container in which it gets injected. Suprise - its
header.container instead of
<move element="navigation.sections" destination="header.container" />