I believe just the view & filters can be customized on Elastic Search.
As far as the actions are concerned, the default behavior of Elastic Search can't be customized as the actions configured on search results are final. (pzSearchResultName).
The system performs "Open Rules by Name" if it's a rule type and "Open Work By Handle" if it's work type (displays the case in review harness with assignments listed).
WorkObject can have multiple flows(PxFlows) & with corresponding assignment keys and to be able to open specific assignments you need to determine the AssignmentKey and pass to OpenAssignment action. This clearly requires separate customization and can't use or alter OOTB Elastic search functionality.