If I assign a worksheet to the variable ws and a range to the variable rng,
why can't I then do a ws.rng.Select?

If I do it in two steps (i.e., ws.Select followed by a rng.Select),
everything works.

Sub test()
   Dim rng As Range
   Dim ws As Worksheet
   
   Worksheets("Sheet1").Select
   Set rng = Range("A1:A10")
   Set ws = Worksheets("Sheet1")

   Worksheets("Sheet2").Select
   
   ws.Select  ' <- OK. Selects Sheet1
   rng.Select ' <- OK. Selects A1:A10 on Sheet1
   
   Worksheets("Sheet2").Select
'   Try to combine ws and rng into one command:
   ws.rng.Select '<- Fails: Method or data member (".rng") not found

End Sub

I get the same behavior with the following code:

Sub test2()
   Dim rng As Range
   Dim str As String
   
   str = "Sheet2!$A$1:$C$5"
   Set rng = Range(str)
   
   Worksheets("Sheet1").Select
'   rng.Select        ' <- Fails: Method 'Select' of object 'Range' failed
   rng.Value = "huh?" ' <- Works OK. Changes values on Sheet2 to "huh?"
End Sub

It seems the Range knows which worksheet it is associated with, but the
address of the range does not include the sheet name, only the range
address. And I can only use the sheet reference inherent in a Range to
change values, not navigate.