4Dv18 changes the locations where some of the MSC logs are generated. In older versions the logs were placed in a Logs folder next to the database's structure. In v18 the logs are now generated in the new following locations:

Mac:
/Users/{User Name}/Library/Application Support/4D/{Database Name}/Logs/

Win:
C:\Users\{User Name}\AppData\Roaming\4D\{Database Name}\Logs\

So when trying to look back at older logs of MSC actions performed in v18+ be sure to check the new location instead of the old one.