A side thought: since there's usually a preview button around when one is submitting a node for the first time, would such a button be desirable when editing a node?
I have wished that it were so, but I have searched for discussions about this, and found much disagreement. As a workaround, you can use your scratchpad to preview anything you care to write.

Update: ... and came across one final question.
In future posts, please consider making this kind of update into a separate reply instead. It will be easier for other monks to follow the conversation. As it is, no one can tell for sure that my second reply was to the pre-update version of your reply, and my third reply was to the post-update version of your reply. It is clear to you and I today, but it will be less clear to future monks searching for enlightenment.

...have the code run, and come up simply as a rectangle that displays all the information (buttons) in one window.
The window manager should do this automatically. After a good night's sleep, I see that I missed something in my last example. Now that we are not displaying all 30 button sets at once, we no longer need the scrolling, and so $pane can be removed, allowing $frame to become a child of $mw. After this change, the application starts up with the correct size. In diff notation:

-my $pane = $mw->Scrolled(qw/Pane -scrollbars osow/)->pack(
-  -expand => 'yes',
-  -fill   => 'both',
-);
-my $frame = $pane->Frame->pack();
+my $frame = $mw->Frame->pack();
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