That is easy ;)
your listbox should contain a @CHUNK yourchunk
In that chunk you can perform nearly everything, that genereates a list, like:
<select name="something" id="something" >
<option value="" selected disabled>choose</option>
<optgroup label="Headline 01">
[[pdoResources? &parents=`0` &where=`{"template:=":40` &sortby=`{"value":"ASC"}` &limit=`40` &tpl=`pdoResourcesFormoption-something` &includeTVs=`some-tv`]]
</optgroup>
<optgroup label="Headline 02">
[[pdoResources? &parents=`0` &where=`{"template:=":41` &sortby=`{"value":"ASC"}` &limit=`40` &tpl=`pdoResourcesFormoption-something` &includeTVs=`some-tv`]]
</optgroup>
<optgroup label="Headline 03">
[[pdoResources? &parents=`0` &where=`{"pagetitle:=":"something"` &sortby=`{"value":"ASC"}` &limit=`40` &tpl=`pdoResourcesFormoption-something` &includeTVs=`some-tv`]]
</optgroup>