Create extension for multiple schema
When, creating any extensions, make sure you do the with schema pg_catalog to have those extensions available for all schemas of the database.
For example, to create the pg_trgm index extension, do as follow once connected to your database. Not having the with schema pg_catalog will lead to the typical ERROR: operator class “gin_trgm_ops” does not exist for access method “gin” on your second schema if you have a multiple schema setup.
mydb=# create extension pg_trgm with schema pg_catalog;
To list installed extensions:
To alter already installed extension
mydb=# ALTER EXTENSION pg_trgm SET SCHEMA pg_catalog;