Create new column from existing columns

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test (later on when you use the query on your dataset, you will have to change the source appropriately. If you have columns other than these, then delete Changed type step and do a Changed type for complete table from UI again)

If you already getting nulls in place of space, then #"Replaced Value" step is not required for you. 

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("Xc47DoAgEATQu1BT8BGB0k+tEUvC/a8hDAtBEpaYvJmVGJlknCnr823yHG3qR+KRqRJwYgjQKaiBcm6H3l4QUC0Q/nUD1aP2SPEVvkzr777dws3Yv2r9gjv4Sr7l2WnHCfdwS/7Uamh/lwLsiPN529vSBw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [id = _t, incident_id = _t, user_id = _t, stander_outcome = _t, recomanded_outcome = _t, override_outcome = _t, final_rcommendation_outcome = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"id", Int64.Type}, {"incident_id", Int64.Type}, {"user_id", Int64.Type}, {"stander_outcome", type text}, {"recomanded_outcome", type text}, {"override_outcome", type text}, {"final_rcommendation_outcome", type text}}),
    #"Replaced Value" = Table.ReplaceValue(#"Changed Type","",null,Replacer.ReplaceValue,{"stander_outcome", "recomanded_outcome", "override_outcome", "final_rcommendation_outcome"}),
    #"Added Custom" = Table.AddColumn(#"Replaced Value", "latest", each List.RemoveNulls({[override_outcome]}&{[final_rcommendation_outcome]}&{[recomanded_outcome]}&{[stander_outcome]}){0})
in
    #"Added Custom"