Hi, I have a hard time trying to understand why you create a canvas, add notebooks to the canvas, and add windows into the canvas to hold the notebooks, $mw->Popup, $mw->withdraw.???? Did you just cut-copy-and-paste a bunch of code together and hoped it worked? :-)

Notebooks are hard to get working properly when it comes to resizing, see: perltk autoresize following users resize

Here is a hack to make it work somewhat correctly, just make your widgets larger, I upped them to 1000. I also didn't pack them until just before the Mainloop is called. This gives them time to size themselves before being displayed.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::NoteBook;
use Tk::Pane;

my $mw = MainWindow->new;
$mw->geometry("600x400");

my $pane = $mw->Scrolled('Pane',-height => 1000,-bg=>'black', -scrollb
+ars => "osoe");
my $n = $pane->NoteBook();
 
for ( 1 .. 20 ){
my $title = "mytab $_";
$_ = create_tab("$title");
}

#pack widgets after being fully built
$n->pack(-expand=> 1, -fill=>'both', -expand=>1, -anchor=>'nw',-side =
+> 'top');
$pane->pack(-fill => 'both', -expand => 1);

$mw->update;

MainLoop;

sub create_tab
{
    my $tabname = shift;

    my $tn = $n->add($tabname, -label => $tabname, -underline => 0,
              #-raisecmd =>sub{ $mw->update}
             );

    my $t = $tn->Scrolled("Text", -scrollbars => "onow", -height=> 100
+0, 
           -bg=> 'lightseagreen',
           -wrap => 'none')->pack(-expand => 1, -fill => 'both', -anch
+or=> 'nw');
    
    $t->tagConfigure ('bold', -font => [ -size => 20, -weight => 'bold
+' ]);
    
    for (1..1000){$t->insert('end',$tabname. "_$_\n",['bold'])};
    
    return $t;
}
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