Is there a way to combine month and year and add city in seperate column transformation using PowerQuery?

Is there a way to achieve this transformation using PowerQuery?

Input table:

Output:

Here is a brute force way of doing it with your sample data schema:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8snPS8nPU9JRAqFYnWglIwNDMyDbKzGvNLGoEsgytASLA1luqUlFUEEjA5igb2JRcgZImTlMxLGgKDMHoQZooDlVDQxILMosHlIuDsrPTR06Do4FAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"City Year" = _t, Month = _t, Value = _t]),
    #"Added Custom" = Table.AddColumn(Source, "City", each if [Month] = "" then [City Year] else null, type text),
    #"Filled Down" = Table.FillDown(#"Added Custom",{"City"}),
    #"Filtered Rows" = Table.SelectRows(#"Filled Down", each ([Month] <> "")),
    #"Replaced Value" = Table.ReplaceValue(#"Filtered Rows","",null,Replacer.ReplaceValue,{"City Year"}),
    #"Filled Down1" = Table.FillDown(#"Replaced Value",{"City Year"}),
    #"Inserted Merged Column" = Table.AddColumn(#"Filled Down1", "Month/Year", each Text.Combine({[Month], [City Year]}, " "), type text),
    #"Removed Other Columns" = Table.SelectColumns(#"Inserted Merged Column",{"City", "Month/Year", "Value"})
in
    #"Removed Other Columns"