Subindexing and Marginal Differencing

Hi Anonymous 

It is possible with Power query. But it is more complicated then my previous answer.

In original table "Table"

1. add an index column by grouped data

https://www.myonlinetraininghub.com/numbering-grouped-data-power-query

2. merge columns to get a new column "Merged1"

3. create a blank query, paste code in Advanced editor

let
    Source =Table,
    #"Filtered Rows" = Table.SelectRows(Source, each ([Custom.new index] <> 1)),
    #"Added Custom" = Table.AddColumn(#"Filtered Rows", "Custom", each [Custom.new index]-1),
    #"Inserted Merged Column" = Table.AddColumn(#"Added Custom", "Merged2", each Text.Combine({[User], Text.From([Date], "en-US"), Text.From([Custom], "en-US")}, " "), type text),
    #"Removed Columns" = Table.RemoveColumns(#"Inserted Merged Column",{"Custom.new index", "Merged1"})
in
    #"Removed Columns"

Reference:

https://community.powerbi.com/t5/Desktop/Move-one-row-up-in-a-particular-column/td-p/624373

4. merge queries to a new queries, add a custom column

let
    Source = Table.NestedJoin(Table, {"Merged1"}, Query1, {"Merged2"}, "Query1", JoinKind.LeftOuter),
    #"Expanded Query1" = Table.ExpandTableColumn(Source, "Query1", {"Custom.Time"}, {"Query1.Custom.Time"}),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded Query1",{"Merged1"}),
    #"Added Custom1" = Table.AddColumn(#"Removed Columns", "Custom.2", each if [Query1.Custom.Time] <> null then [Query1.Custom.Time]-[Custom.Time] else "n/a"),
    #"Changed Type" = Table.TransformColumnTypes(#"Added Custom1",{{"Custom.2", type text}})
in
    #"Changed Type"