I changed 2 lines in site/modules/TemplateNotes/TemplateNotes.module (starts at line 98)
if(ProcessWire::versionMajor == 2 && ProcessWire::versionMinor <= 4)
$form->append($tab);
if(ProcessWire::versionMajor >= 2 && ProcessWire::versionMinor >= 5)
$form->prepend($tab);
to
if(ProcessWire::versionMajor == 3 && ProcessWire::versionMinor <= 4)
$form->append($tab);
if(ProcessWire::versionMajor >= 3 && ProcessWire::versionMinor >= 5)
$form->prepend($tab);
Seems to be working on 3.0.40. Only glitch is the bottom Save button jumps above notes content.