While creating a report / query in Online Report Designer, the "Show Advanced" option is not available.
Reproducing the Issue
Create a query by selecting fields from schemas present in the left side
On the edit page the "Show Advanced" option is not available.
"Show Advanced" is applicable only to Detailed Reporting(Legacy ODS Schemas).
The behaviour is expected.
The feature in not applicable to REALMS / Advanced Reporting.
Show Advanced Query , KBA , LOD-SF-ANA-ADV , Advanced Reporting (ODS) , Problem