I do not see official support mentioned for SQL Server 2017 yet:
https://docs.mendix.com/refguide/system-requirements
The latest I see in the release notes is for Mendix 7.2, which added a JDBC driver that supports up to SQL Server 2016.
https://docs.mendix.com/releasenotes/desktop-modeler/7.2
EDIT: I hear that there is unofficial support for SQL Server 2017 in the latest release (7.15), and official support may be coming soon.