Creating a rank/index column based on conditions in Power Query

I hope i understood you well 🙂

Try this in new query and adjust accordingly.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ndRLDsIwDATQu2TNwp9x7Jyl4gaIHfcniE9bFIHTVUdRn9J4lC5LkRYazuVUrrfLpT8UrO6m6wpABqLgcj4tRVnRavT1lapVgYD2HNrfC+557zZp49YIreqBhnlnIuQx7bx6FZZ5ZxZN6YCDM3z+fEKmcWA/ZZjWn84I+u0y/W3cK+b6G7pEfyOX6WHs/vcwdMBjSvMu0wMbf7tUDxv3jMkeRi7Tw8Cl5jlyk3P5fGeFBz3PJ5VEyXdOWvP+83rfBxP2135C/LhH5zs=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [eventid = _t, prioreventid = _t, pollquestionid = _t, priorquestionid = _t, eventuserid = _t]),
    Grouped = Table.Group(Source, {"eventid", "pollquestionid"}, {{"Gr", each _, type table}}),
    Grouped2 = Table.Group(Grouped, {"eventid"}, {{"Gr2", each _, type table }}),
    AddIndex = Table.AddColumn(Grouped2, "Custom", each Table.AddIndexColumn([Gr2], "Question Number",1,1)),
    Expanded2 = Table.ExpandTableColumn(AddIndex, "Custom", {"Gr", "Question Number"}, {"Gr", "Question Number"}),
    Expanded = Table.ExpandTableColumn(Expanded2, "Gr", {"prioreventid", "pollquestionid", "priorquestionid", "eventuserid"}, {"prioreventid", "pollquestionid", "priorquestionid", "eventuserid"}),
    FINAL = Table.RemoveColumns(Expanded,{"Gr2"})
in
    FINAL