sharepoint List Schema:
Main List: Candidate Name(person/group) ,Grade(dropdown values P1,P2,P3,P4,P5,P6,P7,G3,G4,G5,G6,G7,Others),
ShortlistedList : CandidateName(person/group),Grade(dropdown values P1,P2,P3,P4,P5,P6,P7,G3,G4,G5,G6,G7,Others),
criteria
point 1)HR sharepoint group should able to see the dashboard which would have candidate name,grade field details from shortlisted list
Datsource:shortlisted (sharepoint list)

point 2)HR sharepoint group would be able to add/delete candidates name from Main list in to the above gallery(shortlisted datasource)
How to achieve point2 in the existing gallery shortlisted sharepoint list (Datasource)