querystring.py

from plone.app.querystring.queryparser import getPathByUID, getNavigationRoot

def _multi_path(context, row):
    values = []
    for value in row.values.split():
        if not '/' in value:
            # It must be a UID
            value = '/'.join(getPathByUID(context, value))
        # take care of absolute paths without nav_root
        nav_root = getNavigationRoot(context)
        if not value.startswith(nav_root):
            value = nav_root + value
        values.append(value)
    tmp = {row.index: {'query': values, }}
    print tmp
    return tmp

registry.xml

<!-- Operation Definitions -->
<registry xmlns:i18n="http://xml.zope.org/namespaces/i18n"
          i18n:domain="plone">

    <records interface="plone.app.querystring.interfaces.IQueryOperation"
             prefix="plone.app.querystring.operation.string.multiPath">
        <value key="title" i18n:translate="">Multiple absolute paths</value>
        <value key="description" i18n:translate="">One or more location in the site structure</value>
        <value key="operation">kup.eca.site.querystring._multi_path</value>
        <value key="widget">StringWidget</value>
    </records>

<!-- QueryField declarations  -->
    <records interface="plone.app.querystring.interfaces.IQueryField"
             prefix="plone.app.querystring.field.path">
       <value key="title" i18n:translate="">Location</value>
       <value key="description" i18n:translate="">The location of an item </value>
       <value key="enabled">True</value>
       <value key="sortable">False</value>
       <value key="operations">
            <element>plone.app.querystring.operation.string.relativePath</element>
            <element>plone.app.querystring.operation.string.multiPath</element>
            <element>plone.app.querystring.operation.string.path</element>
            </value>
       <value key="group" i18n:translate="">Metadata</value>
    </records>

</registry>