Creating additional indexes on a table with a columnstore clustered index
You can create additional nonclustered indexes on tables with clustered columnstore indexes, the following script shows this...

CREATE TABLE dbo.T2 (C1 INT NOT NULL, C2 INT, C3 INT);
GO
CREATE CLUSTERED COLUMNSTORE INDEX CCI ON dbo.T2;
GO
CREATE NONCLUSTERED INDEX IX ON dbo.T2 (C2);
GO


I have attempted the same thing using SSMS 16.5.3. It is possible that there is a bug in the version you are using (latest is at https://docs.microsoft.com/en-us/sql/ssms/download-sql-server-management-studio-ssms ).

Consider creating the script using TSQL rather than the GUI to see if you get the same result.