I have the updated to latest version of Heidi, and I installed GIS (postgresql-10-postgis-2.4 )
The log of the heidiSQL shows below.
SET search_path TO 'public', '$user';
SELECT *, pg_table_size(QUOTE_IDENT(t.TABLE_SCHEMA) || '.' || QUOTE_IDENT(t.TABLE_NAME))::bigint AS data_length, pg_relation_size(QUOTE_IDENT(t.TABLE_SCHEMA) || '.' || QUOTE_IDENT(t.TABLE_NAME))::bigint AS index_length, c.reltuples, obj_description(c.oid) AS comment FROM "information_schema"."tables" AS t LEFT JOIN "pg_namespace" n ON t.table_schema = n.nspname LEFT JOIN "pg_class" c ON n.oid = c.relnamespace AND c.relname=t.table_name WHERE t."table_schema"='public';
/* Unknown datatype oid #1034 for "nspacl". Fall back to UNKNOWN. */
/* Unknown datatype oid #1034 for "relacl". Fall back to UNKNOWN. */
/* Unknown datatype oid #1009 for "reloptions". Fall back to UNKNOWN. */
/* Unknown datatype oid #194 for "relpartbound". Fall back to UNKNOWN. */
SELECT "p"."proname", "p"."proargtypes" FROM "pg_catalog"."pg_namespace" AS "n" JOIN "pg_catalog"."pg_proc" AS "p" ON "p"."pronamespace" = "n"."oid" WHERE "n"."nspname"='public';
PS: pgAdmin 4 displays properly