Power Query Unpivot columns: You might want to unpivot data, sometimes called flattening the data, to put it in a matrix format so that all similar values are in one column. This is necessary, for example, to create a chart or a report.
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Note:
Syntax: Table.Unpivot(table as table, pivotColumns as list, attributeColumn as text, valueColumn as text) as table Table.Unpivot translates a set of columns in a table into attribute-value pairs, combined with the rest of the values in each row.
Reference:
https://docs.microsoft.com/en-us/power-query/unpivot-column
https://docs.microsoft.com/en-us/powerquery-m/table-unpivot