Oops, just reread - coffee hasn't yet kicked in - and you can't use that interface to change it to a button; just change the wording. But I'll leave the text in, in case it helps someone else who stumbles on this.
The bit that stands is "Where does the text appear and what output are you using?". Screenshots would probably be good, too.
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It's hard to know without knowing exactly where the text appears and what output you are using. But perhaps the LNG file would be the place to start.
File > Project Settings. Click Advanced.
The LNG File tab list a bunch of interface elements for different outputs and parts of Robohelp. Perhaps try the [Common] section first.
Sorry, I'm talking about the "Show" link that appears when you call a webhelp topic on its own, e.g. via CSH, to show the TOC.
If you add a.whtbtnshow to your topic style sheet, you can style the Show hyperlink as a button.
You can also modify your topic template file (C:\Program Files (x86)\Adobe\Adobe RoboHelp 11\RoboHTML\WebHelp5Ext\template_skin\whst_topics.xml) to show a different link for the topics. But the template syntax is not documented, so that's not an easy way to go.