Could not execute the SQL command. Message returned: ERROR: column pr.proisagg does not exist LINE 1: ...namespace AS ns ON pr.pronamespace = ns.oid WHERE pr.proisag... ^ HINT: Perhaps you meant to reference the column
-- "They that would give up essential liberty for temporary safety deserve neither liberty nor safety." -- Benjamin Franklin
Can you confirm the versions of pgModeler and PG? Pgmodeler 0.91 does not fully support PG 11.x and there is an update in preparation in 0.92 which should. You may want to givi it a try.