It worked.
Thanks a lot, Roland!
This is the code I used, in case anyone is interested:
SELECT @SELECT:LK.ID:ID@,
@SELECT:LK.LOOKUP_CODE:LOOKUP_CODE@,
@SELECT:LK.PARENT_LOOKUP_CODE:PARENT_LOOKUP_CODE@,
@SELECT:LK.PARENT_LOOKUP_CODE || '\\' || LK.NAME:PATH@,
@SELECT:LK.LOOKUP_LEVEL:LOOKUP_LEVEL@,
@SELECT:LK.NAME:NAME@,
@SELECT:LK.DESCRIPTION:DESCRIPTION@,
@SELECT:LK.LAST_UPDATED_DATE:LAST_UPDATED_DATE@,
@SELECT:LANG.LANGUAGE_CODE:LANGUAGE_CODE@,
@SELECT:LANG.ID:LANGUAGE_ID@
FROM
CMN_LOOKUPS_V LK, CMN_LANGUAGES LANG
WHERE
LK.language_code = @WHERE:PARAM:LANGUAGE@
AND LK.LOOKUP_TYPE='INV_STAGE_TYPE'
AND LK.PARENT_LOOKUP_CODE = 'project'
AND LK.IS_ACTIVE=1
AND LANG.LANGUAGE_CODE=LK.LANGUAGE_CODE
AND @FILTER@