Named Range Resizing takes a long time

maybe so

With Range("DevelopmentPlan")
    .Resize(.Rows.Count + 1).Name = "DevelopmentPlan"
End With

for example

Sub ert()
With Range("DevelopmentPlan")
    .Resize(.Rows.Count + 1).Name = "DevelopmentPlan"
End With
With ActiveWorkbook.Names("DevelopmentPlan")
    .RefersToRange.Select
    MsgBox .RefersTo
End With
End Sub