When the widget is first filled with text, though, even if the "East" (right-side) scrollbar appears, the slider bar does not appear. After resizing the whole GUI, however, the ROText window is resized, causing the scrollbar slider to appear as it should have done. Another way to make the slider "pop into view" is to click the left mouse inside the ROText window, and move the mouse outside of the window (still holding the button down).

I can't say for sure if it's your problem, but in many other Text widget scripts ( as you know ), it's often neccessary to do a $text->update to bring text into view.

But this seems to be in the scrolled container that holds the text widget. So maybe you could try

# do a 1 event loop iteration
# process any Tk events like mouse moves/button presses/etc 
 1 while $MW->DoOneEvent( ALL_EVENTS | DONT_WAIT );  

# or even a simple
$mw->update;

#or get the scrollbar and update it
$scrollbar->update
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