The current MSFS Navigraph Navigation Data has a separate installer and does not use the FMS Data Manager.
You download the Navigraph MSFS Navigation Data Update installer from Navigraph Hub
The installer takes about a minute and places the Navigraph Navigation Data Update into MSFS ready for load next time you run MSFS, which will take a little longer first run. The installer then shows a Remove button should you wish to remove the data.
To check if the Navigraph Hub is installed, please see FAQ - MSFS Is the Navigraph Navigation Data for MSFS Installed (updated Sep 2022)?