RESOLUTION
It can be done by modifying /usr/local/sitebuilder/modules/sesubmission/module_data/engines.xml file. For example, if you wish to have Google Spain you need to replace one of the fragments in this file with following code:
<ENGINE CAPTION="Google Spain" ID="google_es" URL="www.google.es/">
<LOGO WIDTH="43" HEIGHT="14" FILE="google.gif" />
<ACTION BASE="http://www.google.es/addurl?">
<PARAMETER NAME="site" VALUE="q" />
<PARAMETER NAME="comment" VALUE="dq" />
</ACTION>
</ENGINE> Don't forget to save a copy of the old file, just in case.