[TASK] Improve custom CE explanation in FSC

Resolves: #85459
Releases: master, 8.7
Change-Id: I1732782fa920ffa0f7bfd42016a45ac6437bff0a
Reviewed-on: https://review.typo3.org/57453


Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Karavas Aristeidis <aristeidis.karavas@gmail.com>
Tested-by: Karavas Aristeidis <aristeidis.karavas@gmail.com>
Reviewed-by: Sybille Peters <sypets@gmx.de>
Tested-by: Sybille Peters <sypets@gmx.de>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>