You can easily add more icons to a pinned toolbar. Search across all configuration files to locate all the occurrences of the following text:
<l:PinnedSearchToolBarButton
It appears in the FRED4_TABITEMS.XML, TED4_TABITEMS.XML, SHELL4_TABITEMS.XML.
Example of adding three more icons to the Fred4 pinned search toolbar
<l:PinnedSearchToolBarButton PinnedSearchIndex="10"/>
<l:PinnedSearchToolBarButton PinnedSearchIndex="11"/>
<l:PinnedSearchToolBarButton PinnedSearchIndex="12"/>
under:
<l:ShellToolBar Name="Search" Band="0" BandIndex="0">
in FRED4_TABITEMS.XML.