If you want to use the Partial search, you still have to add the catalog to this key in geomsearch.cfg as in V11: (An existing index for Partial search is signalized by the Icon.)

[settings]
PartialSearchCatalogs=cat/catalogname

Mind that some additional search functionality in Topology search is only available when Partial search is active, e.g., search for non-full cylinders or spheres. This information is not stored in topo index, but only in partial index and since GeoDb is created from the old indexes, you need to activate partial search for these features.