The newthread-window sould have a new tag (for example vbulletin ): the similar threads hack. A klick on a defined word start a search to find similar threads with the same word.
Add a vbCode for search:
<form action="search.php (http://192.168.1.12:9999/forum/search.php)" method="post" name="findsimilar" target="_blank" >
<input type="hidden" name="titleonly" value="1" id="rb_titleonly_0" />
<input type="hidden" name="s" value="" />
<input type="hidden" name="do" value="process" />
<input type="hidden" name="sortby" value="lastpost" />
<input type="hidden" class="bginput" name="query" size="35" value="" tabindex="1" />
<a href="java script:document.findsimilar.query.value='{param}'; document.findsimilar.submit()">{param}</a>
</form>
Adjust hidden fields / default params as needed. Obviously you could shorten HTML transmitted by putting the form into one place (eg {header} template) in the page and then just using the <A HREF... etc. part in the vbCode itself.
Also you might want to give the link a different css style or append an icon in the vbCode to show users in advance what kind of link this is (a "search similar" link)
Or if you would prefer to have a permanent search box you could insert this in a template, for example the {navbar}
<form action="search.php (http://192.168.1.12:9999/forum/search.php)" method="post" name="findsimilar" target="_blank" >
<input type="hidden" name="titleonly" value="1" id="rb_titleonly_0" />
<input type="hidden" name="s" value="" />
<input type="hidden" name="do" value="process" />
<input type="hidden" name="sortby" value="lastpost" />
<input type="text" class="bginput" name="query" size="35" value="" tabindex="1" />
<input type="submit" class="button" value="Find" accesskey="s" tabindex="4" />
</form>
Your second request is more challenging. I am looking for something similar - see my posts
Wiki like autolinks when posting - for easy crossreferencing (https://vborg.vbsupport.ru/showthread.php?t=56945)
dictionary driven replace/markup of words in posts (https://vborg.vbsupport.ru/showthread.php?t=56947)