I'm pretty sure there is a way to do this with an inline function but this works for me and I think is pretty clear and simple:
let
Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Appelant", type text}, {"Appele", type text}}),
SecondCol = Table.FromList(List.Distinct(#"Changed Type"[Appele]), null, {"Appele"}),
FirstCol = Table.FromList(List.Distinct(#"Changed Type"[Appelant]), null, {"Appelant"}),
Joined = Table.AddColumn(FirstCol, "Appele", each SecondCol),
#"Expanded Appele" = Table.ExpandTableColumn(Joined, "Appele", {"Appele"}, {"Appele"})
in
#"Expanded Appele"
Hope this helps!