As a Site Integrator I want to see a list of rendering issues
currently, when "something goes wrong", the inner page in "Backend mode" stays white and when examining the source code, one can see, for example,
<!-- Exception while rendering page<TYPO3.TYPO3:Page>/body : Cannot cast object of type "TYPO3\Eel\FlowQuery\FlowQuery" to string. -->
I think such happenings should pop through to the user more obviously.