WikiTree Plus Help page has the following which should help
This looks like what you are looking for using the Category Word:
To get Unsourced Orphans from the 19th century the query is:
https://wikitree.sdms.si/default.htm?report=srch1&Query=Unsourced+Orphan+19Cen&MaxProfiles=500&SortOrder=Default&PageSize=10
(You need to press the blue "Get Profiles" button to run the query)