[FEATURE] Collect lost elements and show them separately from backend layout

Resolves: #67884
Releases: master
Change-Id: I7c14886e5dc1c81d7d816e5f2eb5d36afb8cdbf9
Reviewed-on: https://review.typo3.org/53040


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: Riccardo De Contardi <erredeco@gmail.com>
Tested-by: Jasmina Ließmann <code@frauliessmann.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>