My first post here, so greetings to everybody and the best health wishes in these complicated times.
I just realised that TextField and TextArea borders can be only enabled/disabled in the IDE, not on the fly. Tested with 2019r3, Mac and Windows using old .border and new .HasBorder syntax.
Since every control in Windows is considered a window by the framework, this should work on a Textarea/textfield:
Perhaps some iteration of this, I use to remove the border of a window:
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (hwnd As Integer, nIndex As Integer, dwNewLong As Integer) As Integer
Const GWL_STYLE = -16
dim rien as integer = SetWindowLong(self.handle, GWL_STYLE, &H800000)
JulianS may already have that in his bag of tricks