To add a column from the data source by using the Edit Table Properties dialog box If you used a custom M expression to select tables and columns when you initially used the Power Query Editor to import data, you must again use an M expression. In these cases, you can use Power Query Editor to select columns from the source table and add them to the model table. Or, for example, a new AdjustedProfit column was added to the FactSales table at the data source, and you now want to add the same AdjustedProfit column and data to the Sales table in the model. If, for example, when you initially imported from a data source, you used the Transform feature to select a limited number of columns from the source table, you later determine that you need to add another column that exists at the source table, but does not yet exist in the model table. You may, however, later determine a source table has additional columns that you want to add to the model table, or you need to add a calculated column with values derived from a DAX formula. You can also write a Power Query M expression that specifies only certain columns to import.
When using the Get Data to import data from a structured data source table, a new table is created in the model which includes all of the columns in the source table, or if you choose to filter out certain columns by using the Transform feature, only those columns and filtered data you select.
This article describes how to add columns to an existing table.