I'm working with an Azure SQL DW scaled to DW6000 and I want to put a user in the 'SloDWGroupC04' workload group.
However, DW6000 only provides the defaults of smallrc, mediumrc, largerc, and xlargerc resource classes that appear to have C00, C05, C06, and C07 respectively according to the documentation.
Usually I can run EXEC sp_addrolemember 'largerc', 'user' (which would put 'user' in C05) but the workload group C04 doesn't have a role yet.
Do I need to create a role first? How do I go about leveraging the other available workload groups beyond the default roles?
These SloDW* workload groups are internal use only. This generic set of workload groups are mapped to the resource classes (i.e. mediumrc, largerc etc.) depending on the DWU setting. For example, the article you have referenced shows the mapping for DW500. In that case C04 is used for the xlargerc.
Unfortunately you cannot alter the mappings yourself at this time. The mappings are fixed. If you would like to see specific improvements in this area I would encourage you to put your suggestions on the SQLDW feedback page.