Hi, without seeing your full working example I couldn't answer to your specific code, but here is a working example to show you a trick with a Scrolled Tree. Notice that scrolling will not work until the mainloop starts and the widget is visible. The work-around is to use an $widget->update. Also notice that the setting range is between 0 and 1.I hope it helps.

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

my $mw = MainWindow->new;
my $tree = $mw->Scrolled('Tree')->pack(qw/-expand 1 -fill both/);

foreach(1 .. 100) {
      $tree->add($_, -text => "Line $_");
}


# you must update the tree first
# before the yview works
$tree->update;
$tree->yview( moveto => .5 );

# or it will always work from a widget
# command after the gui has visibility

$mw->Button( # always works because you have visibility
    -text    => "move it (this works)",
    -command => sub { $tree->yview( moveto => 1 ); }
)->pack;

MainLoop;
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