Temporary table in pgAdmin
Postgres creates a temporary schema for temporary tables named "pg_temp_#", you can see it with psql...
create temp table mytemptable(name varchar);
select c.relname
from pg_namespace n
join pg_class c on n.oid=c.relnamespace
where n.nspname='pg_temp_1';
You can list your schemas executing "\dn" in psql.
Hope that helps.
Temporary tables live in temporary schemas pg_temp_{№}
that hidden by default in pgAdmin UI.
In pgAdmin(pgAdmin4 at least) you can open preferences pane and switch on this setting:
Display->Show system objects?
to True
This will show hidden schemas with your created temp tables.
PS After changing preference refresh schema tree