filter the dates for last 7 days using powerqueryM

Try making "Latest" a step after #"Changed Type",

 

Latest = List.Max(#"Changed Type[Date Column])

 

Now you can just refer to the Latest variable and not have to worry about the out of scope table reference. You can still refer to #"Changed Type" as a table, even though your prior step was Latest:

 

Table.SelectRows(#"Changed Type", each [Date Column] <= Latest and [Date Column] >= Date.AddDays(Latest, -7))

 

--Nate