Give this a try… create a tiddler containing this button:
<$button class="tc-btn-invisible" actions="<$action-navigate $to='HelloThere' $scroll=no />">
<a href="##TestAnchor">goto ~TestAnchor</a>
</$button>
Then, somewhere in HelloThere, add an anchor, like this:
<a id="#TestAnchor"></a>
When you click on the button, if the HelloThere tiddler is not rendered yet, the $action-navigate will open it in the Story River without scrolling to it (so the button stays visible). Then, click the button AGAIN to trigger the anchor link. Note that, if HelloThere is already in the Story River, then only one click is needed to trigger the anchor link.
Admittedly, its a bit of a hack, but it gets you there.
enjoy,
-e