Hi @Partha18,
You can do so by changing the operator id assigned to the workflow in the xtk:workflowLogin schema. This is applicable if your workflows are scheduled and already in a running state.
If you don't see all your workflows here, then you can do as follows:
Query -->. select all workflow. Next, in a javascript activity, loop through those workflow ids returned in the previous query activity and do the following in the for loop
xtk.workflow.SetLogin(<<workflow-id or internalName>>,<<Login of the operator or empty string as you wish>>);
More details here: https://docs.adobe.com/content/help/en/campaign-classic/technicalresources/api/sm-workflow-SetLogin....