Currently we do not have the ability to search for certificates explicitly in the admin GUI. What we do have is ability to search for end entities.
There is a couple of limitations with the search for end entities, namely the search is performed against the end entity data, and not against the content of certificates issued to the end entity. For example, if there are some changes to subject DN etc for an end entity, searching for old values will not produce any results.
In addition, a lot of customers get confused by the search end entities page, because they end-up believing they are searching for certificate values when specifying criteria in advanced mode (as an example).
In general, customers are usually more interested in searching for a specific certificate than end entity. They may want to know what the end entity is, of course.
It would be nice if we had a dedicated page (or something similar) that would allow us to search explicitly for certificates. We could provide information about those certificates in the results, with a link to end entity that has the certificate.
I know this is kind of long-standing wish, but could not find any previous issue report. Let me know if this one is a duplicate.