If for some reason there is a need to remove a large number of duplicate scheduled workflows

declare @wfId varchar(max)

Select @wfId= [<NameOfNintexContentDataBase>].[dbo].Workflows.WorkflowId
from [<NameOfNintexContentDataBase>].[dbo].Workflows
Where WorkflowName = '<NameOfWorkFLow>' ;

Delete From [<NameOfNintexConfigDatabase].[dbo].WorkflowSchedule
where WorkflowId =@wfId;