Convert columns to rows with dynamic columns

Hallo huynq 

you have to first split der your data into tables, promote headers, combine your tables and then do unpivotother

Here the complete solution

let
	Source = #table
	(
		{"Column1","Column2","Column3","Column4"},
		{
			{"","1/1","1/2","1/3"},	{"A","1","1","2"},	{"B","0","2","3"},	{"C","1","1",""},	{"","2/1","2/2",""},	{"A","1","1",""}
		}
	),
    AddIndex = Table.AddIndexColumn(Source, "Index", 0, 1),
    AddDevideTable = Table.AddColumn(AddIndex, "Devide Table", each if [Column1]="" then [Index] else null),
    FillDownDevideTable = Table.FillDown(AddDevideTable,{"Devide Table"}),
    GroupTables = Table.Group(FillDownDevideTable, {"Devide Table"}, {{"AllRows", each _, type table [Column1=text, Column2=text, Column3=text, Column4=text, Index=number, Devide Table=number]}}),
	MaintainTable = Table.TransformColumns
	(
		GroupTables,
		{
			{
				"AllRows",
				(tableint) =>
				let 
					DeleteIndexDevideTable = Table.RemoveColumns(tableint, {"Index", "Devide Table"}),
					Promote = Table.PromoteHeaders(DeleteIndexDevideTable)
				in 
					Promote
			}
		}
	),
	Combine = Table.Combine
	(
		MaintainTable[AllRows]
	),
    UnpivotOther = Table.UnpivotOtherColumns(Combine, {""}, "Attribute", "Value"),
    FilterNonEmptyValue = Table.SelectRows(UnpivotOther, each ([Value] <> ""))
in
    FilterNonEmptyValue

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Have fun

Jimmy