<$list filter="[all[tiddlers]!is[system]each[creator]get[creator]]" variable="author">
!! <<author>>
<$list filter="[creator<author>!is[system]]">
<$link><$view field="title"/></$link><br/>
</$list>
</$list>\define listbytag(tagn)
<<tagname>> <br/>
<$list filter="[tag<tagname>]">
<$view field="title"/><br/>
</$list>
<br/>
\end
<$list filter="[[Tag 1]] [[Tag 2]]" variable="tagname">
<<listbytag>>
</$list>Something like this might work as a starter.
\define listbytag(tagn)
!! <<tagname>>
<$list filter="[tag<tagname>sort[]]">
* <$link><$view field="title"/></$link>
</$list>
\end
<$list filter="[all[tiddlers]tags[]!is[system]sort[]]" variable="tagname">
<<listbytag>>
</$list>