When trying to add a Filter for a dimension that is already selected on the chart the following message: 'Dimension has already been added to query'.
"Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental."
SAP SuccessFactors HXM Suite
This behavior is an expected behavior. It is not possible to add a filter on the query when it is selected on the query. It is possible to filter on this information as below screenshot below:
Dimension, already, added, query, message, WFA, Investigation , KBA , LOD-SF-WFA , Workforce Analytics & Planning , Problem