If the question pertains to the assignment of Work Leaders to work-orders raised and managed in IFS Cloud using the IFS Cloud work-order then the capability is avaialbe as a command button under the page Structure For WO 

Hi,

The field Work Leader is still there on the Work Order in IFS Cloud. You can use the page Structure for WO as Tony points out to set the value in this field but you can also find the field in Additional Information sub-menu in Prepare Work Order.

The Work Leader is something else then the assignee's on the work task.

The assignee’s on the work task are the one assigned to perform the work whilst the Work Leader is someone overall responsible that the work is carried out (one direct functionality is that the Work Leader is controlling which Permits that can be connected/used on the Work Order).