You can use this code to put a Node in the column header:
B4X:
Sub SetColumnGraphic(tv As TableView, Index As Int, Node As Node)
Dim jo As JavaObject = tv
Dim column As JavaObject = jo.RunMethodJO("getColumns", Null).RunMethod("get", Array(Index))
column.RunMethod("setGraphic", Array(Node))
End Sub
Example:
B4X:
Dim b As Button
b.Initialize("b")
b.SetLayoutAnimated(0, 0, 0, 100, 50)
b.Text = "Click"
SetColumnGraphic(TableView1, 1, b)