As a horse_with_no_name provided, you can search the pg_indexes meta-table to find an index by name with the query:
WHERE indexname LIKE '%NameOfIndexYoureSearchingFor%';
Regarding your second question in the comments on how to delete an index in PostgreSQL, you can script it out with a query like this:
DROP INDEX ...
I came up with this query that returns the same columns as PGAdmin III Status Activity window but alas there is no color-coding of queries running longer than 5-10 seconds and no button that will terminate the query or the connection.
select pid as process_id,
datname as Database,
usename as username,
client_addr as client_address,