Use filter="[^(]+.*"
for selecting all viewnames which don't start with "(" or filter="\w+.*"
for viewnames which starts with a letter, digit or underscore.
Example for testing:
<xe:navigator id="navigator1">
<xe:this.treeNodes>
<xe:dominoViewListTreeNode var="viewName" folders="false"
enabled="true" filter="[^(]+.*"
href="#{javascript:viewName}" />
</xe:this.treeNodes>
</xe:navigator>