This TYPO3 extension brings back sysnotes to the page module. Tested with TYPO3 7/8/9 LTS and TemplaVoilà! Plus https://github.com/pluspol-interactive/templavoilaplus
Install this from TER https://extensions.typo3.org/extension/ppi_templavoila_notes/ or clone this repository to typo3conf/ext/ppi_templavoila_notes:
git clone https://github.com/pluspol-interactive/ppi_templavoila_notes.git