FInd header row dynamically in Query

Try this one might help you
HeaderRowIndex = List.PositionOf(
Table.Column(Sheet, "Column1"),
"KPI ID"
)

Anonymous 
Add a custom column to identify the row containing "KPI ID".
Filter the table to find the row number of the header.
Use that row number to set the headers dynamically.

Try using below M code

m
let
Source = Excel.CurrentWorkbook(){[Name="YourTableName"]}[Content],
#"Added Custom" = Table.AddColumn(Source, "IsHeader", each if Text.Contains([Column1], "KPI ID") then "Header" else null),
#"Added Index" = Table.AddIndexColumn(#"Added Custom", "Index", 0, 1, Int64.Type),
#"Filtered Rows" = Table.SelectRows(#"Added Index", each ([IsHeader] = "Header")),
HeaderRowIndex = Table.FirstValue(#"Filtered Rows")[Index],
#"Removed Custom" = Table.RemoveColumns(#"Added Index",{"IsHeader", "Index"}),
#"Promoted Headers" = Table.PromoteHeaders(Table.Skip(#"Removed Custom", HeaderRowIndex), [PromoteAllScalars=true])
in
#"Promoted Headers"