Power Query Grouped table column names

Hi is there a way to access grouped 'all row' table column names when new columns have been added;

So here I have grouped , added a new column and then removed the group by column , I now would like to use table expand table col

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But I need the column names from within the group, I did make it ia list of tables and then combine which does not require names,
and also ReocrdFieldValues as below, which does work, but is

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But is there a simpler / neater way of doing this, I have attached a workbook with the above examples,

Richard.