lightning:omniChannelWorkFlagUpdated event can be used to notify the agents when they raise or lower the Flag for the Supervisor assistance.

1. Create the following Lightning Aura Component.

Sample Code:

Lightning Aura Component:

<aura:component 
                implements="flexipage:availableForAllPageTypes" 
                access="global" >
    <aura:handler 
                  event="lightning:omniChannelWorkFlagUpdated"
                  action="{! c.onWorkFlagged }"/>
</aura:component>

Lightning Aura Component JavaScript Controller:

( {
    
    onWorkFlagged : function( 
        component, event, helper 
    ) {
        
        let flagBool = event.getParam( 
            'isFlagged' 
        );
        console.log( 
            "Work Flagged?",
            flagBool
        );
        console.log(
            "Updated By",
            event.getParam( 'updatedBy' )
        )
        
        let showToast = $A.get(
            "e.force:showToast"
        );
        showToast.setParams( {
            title : 'Omni-Supervisor Alert',
            type : flagBool ? 'success' : 'warning',
            mode : 'sticky',
            message : flagBool ? 'Flag Raised' : 'Flag Lowered'
        } );
        showToast.fire(); 
        
    }
    
} )

2. Add the Lightning Component as the Utility Item.

Output: